[powerpc] deactivate user_malloc.cc tsan test on powerpc64le

This test fails consistently on Ubuntu 16.xx powerpc64 LE systems.
The cause is being investigated and in the meantime disable it so
the buildbots can run cleanly.

llvm-svn: 293939

compiler-rt/test/tsan/Linux/user_malloc.cc

@@ -1,4 +1,5 @@
 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
+// UNSUPPORTED: powerpc64le
 #include <stdio.h>
 
 // Defined by tsan.