diff --git a/core/Makefile b/core/Makefile
index cc5d868..28edc87 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -815,13 +815,8 @@
 
 # We just build this directly to the install location.
 INSTALLED_RAMDISK_TARGET := $(BUILT_RAMDISK_TARGET)
-$(INSTALLED_RAMDISK_TARGET): PRIVATE_DIRS := debug_ramdisk dev metadata mnt proc second_stage_resources sys
 $(INSTALLED_RAMDISK_TARGET): $(MKBOOTFS) $(INTERNAL_RAMDISK_FILES) $(INSTALLED_FILES_FILE_RAMDISK) | $(COMPRESSION_COMMAND_DEPS)
 	$(call pretty,"Target ramdisk: $@")
-	$(hide) mkdir -p $(addprefix $(TARGET_RAMDISK_OUT)/,$(PRIVATE_DIRS))
-ifeq (true,$(BOARD_USES_GENERIC_KERNEL_IMAGE))
-	$(hide) mkdir -p $(addprefix $(TARGET_RAMDISK_OUT)/first_stage_ramdisk/,$(PRIVATE_DIRS))
-endif
 	$(hide) $(MKBOOTFS) -d $(TARGET_OUT) $(TARGET_RAMDISK_OUT) | $(COMPRESSION_COMMAND) > $@
 
 .PHONY: ramdisk-nodeps
diff --git a/core/android_soong_config_vars.mk b/core/android_soong_config_vars.mk
index 04a055d..69e4679 100644
--- a/core/android_soong_config_vars.mk
+++ b/core/android_soong_config_vars.mk
@@ -28,8 +28,6 @@
 
 $(call add_soong_config_var,ANDROID,TARGET_ENABLE_MEDIADRM_64)
 $(call add_soong_config_var,ANDROID,BOARD_USES_ODMIMAGE)
-$(call add_soong_config_var,ANDROID,BOARD_USES_RECOVERY_AS_BOOT)
-$(call add_soong_config_var,ANDROID,BOARD_BUILD_SYSTEM_ROOT_IMAGE)
 
 # TODO(b/172480615): Remove when platform uses ART Module prebuilts by default.
 ifeq (,$(filter art_module,$(SOONG_CONFIG_NAMESPACES)))
@@ -39,6 +37,13 @@
 ifneq (,$(findstring .android.art,$(TARGET_BUILD_APPS)))
   # Build ART modules from source if they are listed in TARGET_BUILD_APPS.
   SOONG_CONFIG_art_module_source_build := true
+else ifeq (,$(filter-out modules_% mainline_modules_%,$(TARGET_PRODUCT)))
+  # Always build from source for the module targets. This ought to be covered by
+  # the TARGET_BUILD_APPS check above, but there are test builds that don't set it.
+  SOONG_CONFIG_art_module_source_build := true
+else ifdef MODULES_BUILD_FROM_SOURCE
+  # Build from source if other Mainline modules are.
+  SOONG_CONFIG_art_module_source_build := true
 else ifneq (,$(filter true,$(NATIVE_COVERAGE) $(CLANG_COVERAGE)))
   # Always build ART APEXes from source in coverage builds since the prebuilts
   # aren't built with instrumentation.
@@ -51,6 +56,13 @@
   # Fuchsia picks out ART internal packages that aren't available in the
   # prebuilt.
   SOONG_CONFIG_art_module_source_build := true
+else ifeq (,$(filter x86 x86_64,$(HOST_CROSS_ARCH)))
+  # We currently only provide prebuilts for x86 on host. This skips prebuilts in
+  # cuttlefish builds for ARM servers.
+  SOONG_CONFIG_art_module_source_build := true
+else ifneq (,$(filter dex2oatds dex2oats,$(PRODUCT_HOST_PACKAGES)))
+  # Some products depend on host tools that aren't available as prebuilts.
+  SOONG_CONFIG_art_module_source_build := true
 else ifeq (,$(filter com.google.android.art,$(PRODUCT_PACKAGES)))
   # TODO(b/192006406): There is currently no good way to control which prebuilt
   # APEX (com.google.android.art or com.android.art) gets picked for deapexing
@@ -61,7 +73,7 @@
   # This sets the default for building ART APEXes from source rather than
   # prebuilts (in packages/modules/ArtPrebuilt and prebuilt/module_sdk/art) in
   # all other platform builds.
-  SOONG_CONFIG_art_module_source_build ?= true
+  SOONG_CONFIG_art_module_source_build ?= false
 endif
 
 # Apex build mode variables