libFuzzer, OpenBSD support

Summary:
- Enabling libfuzzer on OpenBSD
- OpenBSD can t support asan, msan ... the tests can t be run.

Patch by David CARLIER

Reviewers: eugenis, phosek, vitalybuka

Reviewed By: vitalybuka

Subscribers: srhines, mgorny, krytarowski, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D44877

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@329631 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerExtraCounters.cpp b/FuzzerExtraCounters.cpp
index d98598a..c99cd89 100644
--- a/FuzzerExtraCounters.cpp
+++ b/FuzzerExtraCounters.cpp
@@ -11,7 +11,8 @@
 
 #include "FuzzerDefs.h"
 
-#if LIBFUZZER_LINUX || LIBFUZZER_NETBSD || LIBFUZZER_FREEBSD
+#if LIBFUZZER_LINUX || LIBFUZZER_NETBSD || LIBFUZZER_FREEBSD ||                \
+    LIBFUZZER_OPENBSD
 __attribute__((weak)) extern uint8_t __start___libfuzzer_extra_counters;
 __attribute__((weak)) extern uint8_t __stop___libfuzzer_extra_counters;