Remove D8 make variables.

Bug: 67754178
Test: m -j32 checkbuild && USE_D8=true m -j32 checkbuild

Change-Id: I474e57365a8b2c5ff82b5774cb38e6846454f854
diff --git a/core/config.mk b/core/config.mk
index 2ce064f..5f94802 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -511,12 +511,6 @@
 
 USE_PREBUILT_SDK_TOOLS_IN_PLACE := true
 
-# USE_D8_BY_DEFAULT is the default behavior, use USE_D8 to override.
-USE_D8_BY_DEFAULT := false
-ifndef USE_D8
-  USE_D8 := $(USE_D8_BY_DEFAULT)
-endif
-
 #
 # Tools that are prebuilts for TARGET_BUILD_APPS
 #
@@ -530,12 +524,6 @@
   SIGNAPK_JNI_LIBRARY_PATH := $(HOST_OUT_SHARED_LIBRARIES)
   ZIPALIGN := $(HOST_OUT_EXECUTABLES)/zipalign
 
-  ifeq ($(USE_D8),true)
-    DX := $(HOST_OUT_EXECUTABLES)/d8
-  else
-    DX := $(HOST_OUT_EXECUTABLES)/dx
-  endif
-
 else # TARGET_BUILD_APPS || TARGET_BUILD_PDK
   AIDL := $(prebuilt_sdk_tools_bin)/aidl
   AAPT := $(prebuilt_sdk_tools_bin)/aapt
@@ -546,15 +534,8 @@
   SIGNAPK_JNI_LIBRARY_PATH := $(prebuilt_sdk_tools)/$(HOST_OS)/lib64
   ZIPALIGN := $(prebuilt_sdk_tools_bin)/zipalign
 
-  ifeq ($(USE_D8),true)
-    DX := $(prebuilt_build_tools_wrappers)/d8
-  else
-    DX := $(prebuilt_build_tools_wrappers)/dx
-  endif
 endif # TARGET_BUILD_APPS || TARGET_BUILD_PDK
 
-DX_COMMAND := $(DX) -JXms16M -JXmx2048M
-
 ifeq (,$(TARGET_BUILD_APPS))
   # Use RenderScript prebuilts for unbundled builds but not PDK builds
   LLVM_RS_CC := $(HOST_OUT_EXECUTABLES)/llvm-rs-cc