[libFuzzer] exit without running atexit handlers in libfuzzer's crash…

… handler

Summary:
It's not safe to assume that atexit handlers can be run once the app crashed.

Patch by Jochen Eisinger.

Reviewers: kcc, vitalybuka

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32640

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302076 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Fuzzer/FuzzerLoop.cpp

@@ -199,7 +199,7 @@ void Fuzzer::CrashCallback() {
   Printf("SUMMARY: libFuzzer: deadly signal\n");
   DumpCurrentUnit("crash-");
   PrintFinalStats();
-  exit(Options.ErrorExitCode);
+  _Exit(Options.ErrorExitCode);  // Stop right now.
 }
 
 void Fuzzer::InterruptCallback() {