[libFuzzer] Fix Alarm callback in fuchsia.

Authored by jakehehrlich on Oct 9 2019, 2:01 PM.


[libFuzzer] Fix Alarm callback in fuchsia.

This patch adds an #if macro to skip the InFuzzingThread() comparison
for fuchsia, similar to what it is done for Windows and NetBSD.

In fuchsia, the alarm callback runs in a separate thread[0], making it fail
the comparison InFuzzingThread(), breaking the -timeout flag.


Author: charco (aka Marco Vanotti)
Differential Revision: https://reviews.llvm.org/D68166

llvm-svn: 374228