Use a variable to stop us from building clang testing tools.
<rdar://problem/11202465>


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164739 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/Makefile b/tools/Makefile
index e7aa2fa..f271e13 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -14,6 +14,10 @@
 DIRS := driver libclang c-index-test arcmt-test c-arcmt-test diagtool \
         clang-check
 
+ifeq ($(CLANG_NO_TEST_TOOLS),YES)
+DIRS := driver libclang
+endif
+
 # Recurse into the extra repository of tools if present.
 OPTIONAL_DIRS := extra