asan/msan: fix "unused function 'OnExit'" warning

llvm-svn: 191904
diff --git a/compiler-rt/lib/msan/msan_interceptors.cc b/compiler-rt/lib/msan/msan_interceptors.cc
index 34bb31b..b616b98 100644
--- a/compiler-rt/lib/msan/msan_interceptors.cc
+++ b/compiler-rt/lib/msan/msan_interceptors.cc
@@ -1112,11 +1112,15 @@
   bool in_interceptor_scope;
 };
 
-static int OnExit() {
+namespace __msan {
+
+int OnExit() {
   // FIXME: ask frontend whether we need to return failure.
   return 0;
 }
 
+}  // namespace __msan
+
 // A version of CHECK_UNPOISED using a saved scope value. Used in common
 // interceptors.
 #define CHECK_UNPOISONED_CTX(ctx, x, n)                         \