[test][sanitizer] Disable new test failing on PPC

Author: vitalybuka

compiler-rt/test/sanitizer_common/TestCases/Posix/fork_threaded.c

@@ -3,6 +3,9 @@
 // The test uses pthread barriers which are not available on Darwin.
 // UNSUPPORTED: darwin
 
+// FIXME: It probably hangs on this platform.
+// UNSUPPORTED: ppc
+
 // Forking in multithread environment is unsupported. However we already have
 // some workarounds, and will add more, so this is the test.
 // The test try to check two things: