Add a testcase for r134292.

Part of rdar://9714064


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134295 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/darwin-thread-specifier.c

@@ -0,0 +1,3 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.7.0 -emit-llvm -o - %s | FileCheck %s
+// CHECK: @b = thread_local global i32 5, align 4
+__thread int b = 5;