kbuild: consolidate Clang compiler flags

commit 238bcbc4e07fad2fff99c5b157d0c37ccd4d093c upstream.

Collect basic Clang options such as --target, --prefix, --gcc-toolchain,
-no-integrated-as into a single variable CLANG_FLAGS so that it can be
easily reused in other parts of Makefile.

Change-Id: I60289506aa4b04e31e5f10e4de0a620d489d67b2
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-Commit: 8ff3c2ecc1a4b79d6ee2b0e705784e2619ccaf7d
Git-Repo: https://android.googlesource.com/kernel/common


[schikk: Resolved trivial merge conflicts]
Signed-off-by: Swetha Chikkaboraiah <schikk@codeaurora.org>