Silence unused result warnings in art.

This lets us turn on _FORTIFY_SOURCE=2 for the host.

The logging change is basically a trick (since we're still ignoring the
result unless it's an EINTR failure).

The profiler change is in a function whose error checking is a mess; the
fd is leaked, and it's not clear what's supposed to happen about the flock
on failure. I didn't exit if the ftruncate fails because the rest of the
function just blunders on, and error handling here needs a deeper rethink.

Bug: http://b/20558757
Change-Id: I7a2873fce08e37f4af826a04b4701d7ac6a8e3fa