Disable emulator from platform builds.

Now that emulator prebuilts are available under prebuilts/android-emulator/,
disable building the emulator from source in all platform builds, except
if one defines BUILD_EMULATOR to 'true' in its environment.

NOTE: This patch should be applied after this one to avoid issues
      with the GPU emulation libraries:
            https://android-review.googlesource.com/93980

Change-Id: I53b2ada9ca0c2e159dccee7cdca7f55f6b0d1d42

core/main.mk

@@ -228,22 +228,8 @@ endif
 
 
 ifndef BUILD_EMULATOR
-ifeq (darwin,$(HOST_OS))
+  # Emulator binaries are now provided under prebuilts/android-emulator/
-GCC_REALPATH = $(realpath $(shell which $(HOST_CC)))
-ifneq ($(findstring llvm-gcc,$(GCC_REALPATH)),)
-  # Using LLVM GCC results in a non functional emulator due to it
-  # not honouring global register variables
-  $(warning ****************************************)
-  $(warning * gcc is linked to llvm-gcc which will *)
-  $(warning * not create a useable emulator.       *)
-  $(warning ****************************************)
   BUILD_EMULATOR := false
-else
-  BUILD_EMULATOR := true
-endif
-else   # HOST_OS is not darwin
-  BUILD_EMULATOR := true
-endif  # HOST_OS is darwin
 endif
 
 $(shell echo 'VERSIONS_CHECKED := $(VERSION_CHECK_SEQUENCE_NUMBER)' \

target/board/generic_arm64/BoardConfig.mk

@@ -55,4 +55,3 @@ BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
 BOARD_FLASH_BLOCK_SIZE := 512
 TARGET_USERIMAGES_SPARSE_EXT_DISABLED := true
 
-BUILD_EMULATOR := false