Suppress clang warnings which fire often in musl.

musl isn't interested in fixing these, they assume that people know the
language that musl is written in :-)

Ideally we'd only suppress them for musl files, but since there's
currently no good way to do this suppress them globally. Having a
low-noise build has a higher value than these warnings for the ndk.

Change-Id: I5cd9f428529a0a455ff6ce90a27bde7b8028afca