Summary:
Fixes https://github.com/google/sanitizers/issues/788/, a deadlock
caused by multiple crashes happening at the same time. Before printing
a crash report, we now test and set an atomic flag. If the flag was
already set, the crash handler returns immediately.
Reviewers: kcc
Reviewed By: kcc
Subscribers: llvm-commits, kubamracek
Differential Revision: https://reviews.llvm.org/D46277
llvm-svn: 331310