Fix android_arm64 target for experimental ndk

Makefile.android

Index: Makefile.android
diff --git a/Makefile.android b/Makefile.android
index f4e144f280f280b356ce92de02d26229ef408d01..b3a3a152d4faffab9e82ef326e507ac865a79dce 100644
--- a/Makefile.android
+++ b/Makefile.android
@@ -47,20 +47,20 @@ else
 endif
 
 ifeq ($(ARCH), android_arm)
-  DEFINES  = target_arch=arm v8_target_arch=arm android_target_arch=arm
+  DEFINES  = target_arch=arm v8_target_arch=arm android_target_arch=arm android_target_platform=9
   DEFINES += arm_neon=0 arm_version=7
   TOOLCHAIN_ARCH = arm-linux-androideabi
   TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
   TOOLCHAIN_VER = 4.6
 else
   ifeq ($(ARCH), android_arm64)
-    DEFINES  = target_arch=arm64 v8_target_arch=arm64 android_target_arch=arm64
+    DEFINES  = target_arch=arm64 v8_target_arch=arm64 android_target_arch=arm64 android_target_platform=20
     TOOLCHAIN_ARCH = aarch64-linux-android
     TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
     TOOLCHAIN_VER = 4.8
   else
     ifeq ($(ARCH), android_mipsel)
-      DEFINES  = target_arch=mipsel v8_target_arch=mipsel
+      DEFINES  = target_arch=mipsel v8_target_arch=mipsel android_target_platform=9
       DEFINES += android_target_arch=mips mips_arch_variant=mips32r2
       TOOLCHAIN_ARCH = mipsel-linux-android
       TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
@@ -68,7 +68,7 @@ else
 
     else
       ifeq ($(ARCH), android_ia32)
-        DEFINES = target_arch=ia32 v8_target_arch=ia32 android_target_arch=x86
+        DEFINES = target_arch=ia32 v8_target_arch=ia32 android_target_arch=x86 android_target_platform=9
         TOOLCHAIN_ARCH = x86
         TOOLCHAIN_PREFIX = i686-linux-android
         TOOLCHAIN_VER = 4.6