kernel_definitions: allow using custom LLVM toolchain for the kernel

Device can opt-in via roomservice's revision set for
prebuilts/clang-standalone and KERNEL_CUSTOM_LLVM := true from
BoardConfig.mk.

Change-Id: Ic4dc6328f24afaccb03ccb819e3b79c6169fd193
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
1 file changed