ANDROID: kleaf: convert rockpi4 to mixed build.

Build the GKI //common:kernel_aarch64, then
build rockpi4 modules on top of it.

As a side effect of this change, rockpi4 will no longer
be able to be built with build.sh because it won't produce
vmlinux, etc..

Test: TH
Test: bazel run //common:rockpi4_dist
Bug: 258841346
Change-Id: I88989a265d0a90daddc85dd45a8736f942350522
Signed-off-by: Yifan Hong <elsk@google.com>

build.config.rockpi4

@@ -10,10 +10,11 @@ FRAGMENT_CONFIG=${KERNEL_DIR}/arch/arm64/configs/rockpi4_gki.fragment
 PRE_DEFCONFIG_CMDS="KCONFIG_CONFIG=${ROOT_DIR}/${KERNEL_DIR}/arch/arm64/configs/${DEFCONFIG} ${ROOT_DIR}/${KERNEL_DIR}/scripts/kconfig/merge_config.sh -m -r ${ROOT_DIR}/${KERNEL_DIR}/arch/arm64/configs/gki_defconfig ${ROOT_DIR}/${FRAGMENT_CONFIG}"
 POST_DEFCONFIG_CMDS="rm ${ROOT_DIR}/${KERNEL_DIR}/arch/arm64/configs/${DEFCONFIG}"
 
-MAKE_GOALS="${MAKE_GOALS}
+MAKE_GOALS="
+modules
 rockchip/rk3399-rock-pi-4b.dtb
 "
 
-FILES="${FILES}
+FILES="
 arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dtb
 "