[macOS] Darwin doesn't support MSG_NOSIGNAL
[macOS] Darwin doesn't support MSG_NOSIGNAL

Darwin supports SO_NOSIGPIPE the BSD way. So when available fail over to it
via a setsockopt set. Otherwise abort with a compilation error. The same code
should also work for bsd based setups.

libcommon/files.c:159:68: error: use of undeclared identifier 'MSG_NOSIGNAL'
        ssize_t sz = send(fd, &buf[writtenSz], fileSz - writtenSz, MSG_NOSIGNAL | MSG_DONTWAIT);

Signed-off-by: Anestis Bechtsoudis <7611fa5e9fd33f993ed88a8464a47644a6f066ca@census-labs.com>

google/honggfuzz,google/honggfuzz,anestisb/honggfuzz,google/honggfuzz