Build TaskQueueTest in threads=on builds, fixes regression from r335608.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335724 91177308-0d34-0410-b5e6-96231b3b80d8

Author: nico

unittests/Support/TaskQueueTest.cpp

@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Config/llvm-config.h"
+
 #if LLVM_ENABLE_THREADS
 
 #include "llvm/Support/TaskQueue.h"