build: enable defconfig check

Change-Id: I976a2700c7b03ca9b0d340ef0e4b50f2bb272cff
Signed-off-by: Patrick Tjin <pattjin@google.com>

build.config

@@ -4,6 +4,7 @@ CROSS_COMPILE=aarch64-linux-android-
 DEFCONFIG=angler_defconfig
 EXTRA_CMDS=''
 KERNEL_DIR=private/msm-huawei
+POST_DEFCONFIG_CMDS="check_defconfig"
 LINUX_GCC_CROSS_COMPILE_PREBUILTS_BIN=prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin
 FILES="
 arch/arm64/boot/Image.gz-dtb