android_x86_64: Set arch variant to sandybridge

This has the same instruction set definitions as default,
according to `build/soong/android/arch_list.go`.

Fixes:
W tion.vmlauncher: Unexpected CPU variant for x86: x86_64.
W tion.vmlauncher: Known variants: atom, sandybridge, silvermont, goldmont, goldmont-plus, goldmont-without-sha-xsaves, tremont, kabylake, default

Change-Id: I70e3683a5be4455ced3abedba9c239705394d027

Author: me-cafebabe

BoardConfig.mk

@@ -6,11 +6,11 @@
 TARGET_NO_BOOTLOADER := true
 TARGET_CPU_ABI := x86_64
 TARGET_ARCH := x86_64
-TARGET_ARCH_VARIANT := x86_64
+TARGET_ARCH_VARIANT := sandybridge
 
 TARGET_2ND_CPU_ABI := x86
 TARGET_2ND_ARCH := x86
-TARGET_2ND_ARCH_VARIANT := x86_64
+TARGET_2ND_ARCH_VARIANT := sandybridge
 
 ifeq ($(USE_LIBNDK_TRANSLATION_NB),true)
 include vendor/google/emu-x86/board/native_bridge_arm_on_x86.mk