diff --git a/CleanSpec.mk b/CleanSpec.mk
index 88f9172..b955e25 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -417,6 +417,9 @@
 # Soong module variant change, remove obsolete intermediates
 $(call add-clean-step, rm -rf $(OUT_DIR)/soong/.intermediates)
 
+# Version checking moving to Soong
+$(call add-clean-step, rm -rf $(OUT_DIR)/versions_checked.mk)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************
diff --git a/core/cleanbuild.mk b/core/cleanbuild.mk
index fa89758..b7109f6 100644
--- a/core/cleanbuild.mk
+++ b/core/cleanbuild.mk
@@ -14,7 +14,7 @@
 #
 
 # Don't bother with the cleanspecs if you are running mm/mmm
-ifeq ($(ONE_SHOT_MAKEFILE)$(dont_bother),)
+ifeq ($(ONE_SHOT_MAKEFILE)$(dont_bother)$(NO_ANDROID_CLEANSPEC),)
 
 INTERNAL_CLEAN_STEPS :=
 
@@ -142,53 +142,7 @@
 INTERNAL_CLEAN_STEPS :=
 INTERNAL_CLEAN_BUILD_VERSION :=
 
-endif  # if not ONE_SHOT_MAKEFILE dont_bother
-
-# Since products and build variants (unfortunately) share the same
-# PRODUCT_OUT staging directory, things can get out of sync if different
-# build configurations are built in the same tree.  The following logic
-# will notice when the configuration has changed and remove the files
-# necessary to keep things consistent.
-
-previous_build_config_file := $(PRODUCT_OUT)/previous_build_config.mk
-current_build_config_file := $(PRODUCT_OUT)/current_build_config.mk
-
-current_build_config := \
-    $(TARGET_PRODUCT)-$(TARGET_BUILD_VARIANT)
-force_installclean := false
-
-# Read the current state from the file, if present.
-# Will set PREVIOUS_BUILD_CONFIG.
-#
-PREVIOUS_BUILD_CONFIG :=
--include $(previous_build_config_file)
-PREVIOUS_BUILD_CONFIG := $(strip $(PREVIOUS_BUILD_CONFIG))
-
-ifdef PREVIOUS_BUILD_CONFIG
-  ifneq ($(current_build_config),$(PREVIOUS_BUILD_CONFIG))
-    $(info *** Build configuration changed: "$(PREVIOUS_BUILD_CONFIG)" -> "$(current_build_config)")
-    ifneq ($(DISABLE_AUTO_INSTALLCLEAN),true)
-      force_installclean := true
-    else
-      $(info DISABLE_AUTO_INSTALLCLEAN is set; skipping auto-clean. Your tree may be in an inconsistent state.)
-    endif
-  endif
-endif  # else, this is the first build, so no need to clean.
-
-# Write the new state to the file.
-#
-$(shell \
-  mkdir -p $(dir $(current_build_config_file)) && \
-  echo "PREVIOUS_BUILD_CONFIG := $(current_build_config)" > \
-      $(current_build_config_file) \
- )
-$(shell cmp $(current_build_config_file) $(previous_build_config_file) > /dev/null 2>&1 || \
-  mv -f $(current_build_config_file) $(previous_build_config_file))
-
-PREVIOUS_BUILD_CONFIG :=
-previous_build_config_file :=
-current_build_config_file :=
-current_build_config :=
+endif  # if not ONE_SHOT_MAKEFILE dont_bother NO_ANDROID_CLEANSPEC
 
 #
 # installclean logic
@@ -272,14 +226,6 @@
 	$(hide) rm -rf $(FILES)
 	@echo "Deleted images and staging directories."
 
-ifeq ($(force_installclean),true)
-  $(info *** Forcing "make installclean"...)
-  $(info *** rm -rf $(dataclean_files) $(installclean_files))
-  $(shell rm -rf $(dataclean_files) $(installclean_files))
-  $(info *** Done with the cleaning, now starting the real build.)
-endif
-force_installclean :=
-
 ###########################################################
 
 .PHONY: clean-jack-files
diff --git a/core/config.mk b/core/config.mk
index 583909d..badb9b1 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -492,7 +492,16 @@
 BCC_COMPAT := $(HOST_OUT_EXECUTABLES)/bcc_compat
 DEPMOD := $(HOST_OUT_EXECUTABLES)/depmod
 
+#TODO: use a smaller -Xmx value for most libraries;
+#      only core.jar and framework.jar need a heap this big.
+ifndef DX_ALT_JAR
 DX := $(HOST_OUT_EXECUTABLES)/dx
+DX_COMMAND := $(DX) -JXms16M -JXmx2048M
+else
+DX := $(DX_ALT_JAR)
+DX_COMMAND := java -Xms16M -Xmx2048M -jar $(DX)
+endif
+
 MAINDEXCLASSES := $(HOST_OUT_EXECUTABLES)/mainDexClasses
 
 SOONG_ZIP := $(SOONG_HOST_OUT_EXECUTABLES)/soong_zip
@@ -847,7 +856,7 @@
 
 # These goals don't need to collect and include Android.mks/CleanSpec.mks
 # in the source tree.
-dont_bother_goals := clean clobber dataclean installclean \
+dont_bother_goals := dataclean installclean \
     help out \
     snod systemimage-nodeps \
     stnod systemtarball-nodeps \
diff --git a/core/definitions.mk b/core/definitions.mk
index 64bdfe6..804f2c3 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -2546,14 +2546,11 @@
 endef
 
 
-#TODO: use a smaller -Xmx value for most libraries;
-#      only core.jar and framework.jar need a heap this big.
 define transform-classes.jar-to-dex
 @echo "target Dex: $(PRIVATE_MODULE)"
 @mkdir -p $(dir $@)
 $(hide) rm -f $(dir $@)classes*.dex
-$(hide) $(DX) \
-    -JXms16M -JXmx2048M \
+$(hide) $(DX_COMMAND) \
     --dex --output=$(dir $@) \
     --min-sdk-version=$(call codename-or-sdk-to-sdk,$(PRIVATE_DEFAULT_APP_TARGET_SDK)) \
     $(if $(NO_OPTIMIZE_DX), \
diff --git a/core/host_java_library.mk b/core/host_java_library.mk
index 35dece4..d30c90d 100644
--- a/core/host_java_library.mk
+++ b/core/host_java_library.mk
@@ -76,9 +76,11 @@
         $(proto_java_sources_file_stamp) \
         $(annotation_processor_deps) \
         $(NORMALIZE_PATH) \
+        $(ZIPTIME) \
         $(LOCAL_ADDITIONAL_DEPENDENCIES) \
         | $(SOONG_JAVAC_WRAPPER)
 	$(transform-host-java-to-package)
+	$(remove-timestamps-from-package)
 
 javac-check : $(full_classes_compiled_jar)
 javac-check-$(LOCAL_MODULE) : $(full_classes_compiled_jar)
diff --git a/core/main.mk b/core/main.mk
index 6089cec..f22e63d 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -88,146 +88,6 @@
 # Include the google-specific config
 -include vendor/google/build/config.mk
 
-VERSION_CHECK_SEQUENCE_NUMBER := 6
-JAVA_NOT_REQUIRED_CHECKED :=
--include $(OUT_DIR)/versions_checked.mk
-ifneq ($(VERSION_CHECK_SEQUENCE_NUMBER)$(JAVA_NOT_REQUIRED),$(VERSIONS_CHECKED)$(JAVA_NOT_REQUIRED_CHECKED))
-
-$(info Checking build tools versions...)
-
-# check for a case sensitive file system
-ifneq (a,$(shell mkdir -p $(OUT_DIR) ; \
-                echo a > $(OUT_DIR)/casecheck.txt; \
-                    echo B > $(OUT_DIR)/CaseCheck.txt; \
-                cat $(OUT_DIR)/casecheck.txt))
-$(warning ************************************************************)
-$(warning You are building on a case-insensitive filesystem.)
-$(warning Please move your source tree to a case-sensitive filesystem.)
-$(warning ************************************************************)
-$(error Case-insensitive filesystems not supported)
-endif
-
-# Make sure that there are no spaces in the absolute path; the
-# build system can't deal with them.
-ifneq ($(words $(shell pwd)),1)
-$(warning ************************************************************)
-$(warning You are building in a directory whose absolute path contains)
-$(warning a space character:)
-$(warning $(space))
-$(warning "$(shell pwd)")
-$(warning $(space))
-$(warning Please move your source tree to a path that does not contain)
-$(warning any spaces.)
-$(warning ************************************************************)
-$(error Directory names containing spaces not supported)
-endif
-
-ifneq ($(JAVA_NOT_REQUIRED),true)
-java_version_str := $(shell unset _JAVA_OPTIONS && java -version 2>&1)
-javac_version_str := $(shell unset _JAVA_OPTIONS && javac -version 2>&1)
-
-# Check for the correct version of java, should be 1.8 by
-# default and only 1.7 if LEGACY_USE_JAVA7 is set.
-ifeq ($(LEGACY_USE_JAVA7),) # if LEGACY_USE_JAVA7 == ''
-required_version := "1.8.x"
-required_javac_version := "1.8"
-java_version := $(shell echo '$(java_version_str)' | grep '[ "]1\.8[\. "$$]')
-javac_version := $(shell echo '$(javac_version_str)' | grep '[ "]1\.8[\. "$$]')
-else
-required_version := "1.7.x"
-required_javac_version := "1.7"
-java_version := $(shell echo '$(java_version_str)' | grep '^java .*[ "]1\.7[\. "$$]')
-javac_version := $(shell echo '$(javac_version_str)' | grep '[ "]1\.7[\. "$$]')
-endif # if LEGACY_USE_JAVA7 == ''
-
-ifeq ($(strip $(java_version)),)
-$(info ************************************************************)
-$(info You are attempting to build with the incorrect version)
-$(info of java.)
-$(info $(space))
-$(info Your version is: $(java_version_str).)
-$(info The required version is: $(required_version))
-$(info $(space))
-$(info Please follow the machine setup instructions at)
-$(info $(space)$(space)$(space)$(space)https://source.android.com/source/initializing.html)
-$(info ************************************************************)
-$(error stop)
-endif
-
-# Check for the current JDK.
-#
-# For Java 1.7/1.8, we require OpenJDK on linux and Oracle JDK on Mac OS.
-requires_openjdk := false
-ifeq ($(BUILD_OS),linux)
-requires_openjdk := true
-endif
-
-
-# Check for the current jdk
-ifeq ($(requires_openjdk), true)
-# The user asked for openjdk, so check that the host
-# java version is really openjdk and not some other JDK.
-ifeq ($(shell echo '$(java_version_str)' | grep -i openjdk),)
-$(info ************************************************************)
-$(info You asked for an OpenJDK based build but your version is)
-$(info $(java_version_str).)
-$(info ************************************************************)
-$(error stop)
-endif # java version is not OpenJdk
-else # if requires_openjdk
-ifneq ($(shell echo '$(java_version_str)' | grep -i openjdk),)
-$(info ************************************************************)
-$(info You are attempting to build with an unsupported JDK.)
-$(info $(space))
-$(info You use OpenJDK but only Sun/Oracle JDK is supported.)
-$(info Please follow the machine setup instructions at)
-$(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)
-$(info ************************************************************)
-$(error stop)
-endif # java version is not Sun Oracle JDK
-endif # if requires_openjdk
-
-KNOWN_INCOMPATIBLE_JAVAC_VERSIONS := google
-incompat_javac := $(foreach v,$(KNOWN_INCOMPATIBLE_JAVAC_VERSIONS),$(findstring $(v),$(javac_version_str)))
-ifneq ($(incompat_javac),)
-javac_version :=
-endif
-
-# Check for the correct version of javac
-ifeq ($(strip $(javac_version)),)
-$(info ************************************************************)
-$(info You are attempting to build with the incorrect version)
-$(info of javac.)
-$(info $(space))
-$(info Your version is: $(javac_version_str).)
-ifneq ($(incompat_javac),)
-$(info This '$(incompat_javac)' version is not supported for Android platform builds.)
-$(info Use a publicly available JDK and make sure you have run envsetup.sh / lunch.)
-else
-$(info The required version is: $(required_javac_version))
-endif
-$(info $(space))
-$(info Please follow the machine setup instructions at)
-$(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)
-$(info ************************************************************)
-$(error stop)
-endif
-
-endif # if JAVA_NOT_REQUIRED
-
-ifndef BUILD_EMULATOR
-  # Emulator binaries are now provided under prebuilts/android-emulator/
-  BUILD_EMULATOR := false
-endif
-
-$(shell echo 'VERSIONS_CHECKED := $(VERSION_CHECK_SEQUENCE_NUMBER)' \
-        > $(OUT_DIR)/versions_checked.mk)
-$(shell echo 'BUILD_EMULATOR ?= $(BUILD_EMULATOR)' \
-        >> $(OUT_DIR)/versions_checked.mk)
-$(shell echo 'JAVA_NOT_REQUIRED_CHECKED := $(JAVA_NOT_REQUIRED)' \
-        >> $(OUT_DIR)/versions_checked.mk)
-endif
-
 # These are the modifier targets that don't do anything themselves, but
 # change the behavior of the build.
 # (must be defined before including definitions.make)
@@ -1270,14 +1130,6 @@
 .PHONY: findbugs
 findbugs: $(INTERNAL_FINDBUGS_HTML_TARGET) $(INTERNAL_FINDBUGS_XML_TARGET)
 
-.PHONY: clean
-clean:
-	@rm -rf $(OUT_DIR)/*
-	@echo "Entire build directory removed."
-
-.PHONY: clobber
-clobber: clean
-
 # The rules for dataclean and installclean are defined in cleanbuild.mk.
 
 #xxx scrape this from ALL_MODULE_NAME_TAGS
diff --git a/core/tasks/build_custom_images.mk b/core/tasks/build_custom_images.mk
index 8ebf89b..c5f2a96 100644
--- a/core/tasks/build_custom_images.mk
+++ b/core/tasks/build_custom_images.mk
@@ -54,6 +54,8 @@
   CUSTOM_IMAGE_SELINUX \
   CUSTOM_IMAGE_SUPPORT_VERITY \
   CUSTOM_IMAGE_VERITY_BLOCK_DEVICE \
+  CUSTOM_IMAGE_AVB_ENABLE \
+  CUSTOM_IMAGE_AVB_ADD_HASHTREE_FOOTER_ARGS \
 
 # We don't expect product makefile to inherit/override PRODUCT_CUSTOM_IMAGE_MAKEFILES,
 # so we don't put it in the _product_var_list.
diff --git a/core/tasks/tools/build_custom_image.mk b/core/tasks/tools/build_custom_image.mk
index f0db476..f916e86 100644
--- a/core/tasks/tools/build_custom_image.mk
+++ b/core/tasks/tools/build_custom_image.mk
@@ -74,6 +74,11 @@
 $(my_built_custom_image): PRIVATE_VERITY_KEY := $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VERITY_SIGNING_KEY)
 $(my_built_custom_image): PRIVATE_VERITY_BLOCK_DEVICE := $(CUSTOM_IMAGE_VERITY_BLOCK_DEVICE)
 $(my_built_custom_image): PRIVATE_DICT_FILE := $(CUSTOM_IMAGE_DICT_FILE)
+$(my_built_custom_image): PRIVATE_AVB_ENABLE := $(CUSTOM_IMAGE_AVB_ENABLE)
+$(my_built_custom_image): PRIVATE_AVB_ADD_HASHTREE_FOOTER_ARGS := $(CUSTOM_IMAGE_AVB_ADD_HASHTREE_FOOTER_ARGS)
+ifeq (true,$(CUSTOM_IMAGE_AVB_ENABLE))
+  $(my_built_custom_image): $(AVBTOOL)
+endif
 $(my_built_custom_image): $(INTERNAL_USERIMAGES_DEPS) $(my_built_modules) $(my_image_copy_files) \
   $(CUSTOM_IMAGE_DICT_FILE)
 	@echo "Build image $@"
@@ -97,6 +102,11 @@
 	    echo "verity_key=$(PRIVATE_VERITY_KEY)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt;\
 	    echo "verity_signer_cmd=$(VERITY_SIGNER)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt;\
 	    echo "verity_block_device=$(PRIVATE_VERITY_BLOCK_DEVICE)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt)
+	$(if $(PRIVATE_AVB_ENABLE),\
+	  $(hide) echo "avb_enable=$(PRIVATE_AVB_ENABLE)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt;\
+	    echo "avb_avbtool=$(AVBTOOL)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt;\
+	    echo "avb_signing_args=$(INTERNAL_AVB_SIGNING_ARGS)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt;\
+	    echo "avb_add_hashtree_footer_args=$(PRIVATE_AVB_ADD_HASHTREE_FOOTER_ARGS)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt)
 	$(if $(PRIVATE_DICT_FILE),\
 	  $(hide) echo "# Properties from $(PRIVATE_DICT_FILE)" >> $(PRIVATE_INTERMEDIATES)/image_info.txt;\
 	    cat $(PRIVATE_DICT_FILE) >> $(PRIVATE_INTERMEDIATES)/image_info.txt)