[libFuzzer] Disable print-func.test on Darwin.

The try-lock guard change seems to be making this test fail on Mac, but
I haven't been able to reproduce the failure.  Disabling the test on Mac
to fix build bot.

llvm-svn: 331894

compiler-rt/test/fuzzer/print-func.test

@@ -1,3 +1,4 @@
+UNSUPPORTED: darwin
 RUN: %cpp_compiler %S/PrintFuncTest.cpp -o %t
 RUN: %t -seed=1 -runs=100000 2>&1 | FileCheck %s
 RUN: %t -seed=1 -runs=100000 -print_funcs=0 2>&1 | FileCheck %s --check-prefix=NO