[compiler-rt] Suppress -Wunused-result due to ::write when _FORTIFY_SOURCE>0 in glibc

Noticed by Peter Foley.
In glibc, ::write is declared as __attribute__((__warn_unused_result__)) when __USE_FORTIFY_LEVEL is larger than 0.

GitOrigin-RevId: 1ef0e94d5b0206f69e4e822c6828d0b5121c11fb
1 file changed