Add m4 to non-clangable list
Add m4 to non-clangable list

regressed with clang 4.0.0

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

kraj/meta-clang,kraj/meta-clang,kraj/meta-clang