ANDROID: Makefile: Properly resolve 4.19.35 merge

The merge removed commit 4c451dba ("ANDROID: Kbuild, LLVMLinux:
allow overriding clang target triple").

This keeps commit f66a52d9 ("kbuild: clang: choose GCC_TOOLCHAIN_DIR
not on LD"), which caused the conflict.

Change-Id: I72b7f69204a801ff6ef6405e24317a7b08428901
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>