[profile] Mark instrprof-gcov-fork.test UNSUPPORTED on Darwin as well

This test remains flaky everywhere, I think. We should consider deleting
it and accompanying support code in GCOVProfiling: I've stopped short of
doing that now as the gcov exec* tests appear to be stable.

See the thread re: r347779.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@373121 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/profile/Posix/instrprof-gcov-fork.test b/test/profile/Posix/instrprof-gcov-fork.test
index 5a406fd..31b6a23 100644
--- a/test/profile/Posix/instrprof-gcov-fork.test
+++ b/test/profile/Posix/instrprof-gcov-fork.test
@@ -1,4 +1,5 @@
 UNSUPPORTED: linux
+UNSUPPORTED: darwin
 
 RUN: mkdir -p %t.d
 RUN: cd %t.d