Fix ARM64 build

Makefile.android

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 33 matching lines @@
   $(error Host platform "${HOST_OS}" is not supported)
 endif
 
 ifeq ($(ARCH), android_arm)
   DEFINES  = target_arch=arm v8_target_arch=arm android_target_arch=arm android_target_platform=14
   DEFINES += arm_neon=0 arm_version=7
   TOOLCHAIN_ARCH = arm-linux-androideabi
   TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
   TOOLCHAIN_VER = 4.8
 else ifeq ($(ARCH), android_arm64)
-  DEFINES  = target_arch=arm64 v8_target_arch=arm64 android_target_arch=arm64 android_target_platform=L
+  DEFINES  = target_arch=arm64 v8_target_arch=arm64 android_target_arch=arm64 android_target_platform=21
   TOOLCHAIN_ARCH = aarch64-linux-android
   TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
   TOOLCHAIN_VER = 4.9
 else ifeq ($(ARCH), android_mipsel)
   DEFINES  = target_arch=mipsel v8_target_arch=mipsel android_target_platform=14
   DEFINES += android_target_arch=mips mips_arch_variant=mips32r2
   TOOLCHAIN_ARCH = mipsel-linux-android
   TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
   TOOLCHAIN_VER = 4.8
 else ifeq ($(ARCH), android_ia32)
@@ skipping 41 matching lines @@
 ANDROID_MAKEFILES = $(addprefix $(OUTDIR)/Makefile.,$(ANDROID_BUILDS))
 $(ANDROID_MAKEFILES):
         GYP_GENERATORS=make-android \
         GYP_DEFINES="${DEFINES}" \
         CC="${ANDROID_TOOLCHAIN}/bin/${TOOLCHAIN_PREFIX}-gcc" \
         CXX="${ANDROID_TOOLCHAIN}/bin/${TOOLCHAIN_PREFIX}-g++" \
         PYTHONPATH="$(shell pwd)/tools/generate_shim_headers:$(shell pwd)/build:$(PYTHONPATH)" \
         build/gyp/gyp --generator-output="${OUTDIR}" build/all.gyp \
                       -Ibuild/standalone.gypi --depth=. -Ibuild/android.gypi \
                       -S$(suffix $(basename $@))$(suffix $@) ${GYPFLAGS}