restore proper valgrind support.
disclaim: I know nothing about Python, so apologies in advance if I break something

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@75368 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Makefile b/test/Makefile
index 635759f..4c65d7c 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -12,9 +12,15 @@
 endif
 endif
 
+ifdef VG
+  VGARG="--vg"
+else
+  VGARG=
+endif
+
 all::
 	@ echo '--- Running clang tests for $(TARGET_TRIPLE) ---'
-	@ PATH=$(ToolDir):$(LLVM_SRC_ROOT)/test/Scripts:$$PATH VG=$(VG) $(PROJ_SRC_DIR)/../utils/test/MultiTestRunner.py $(TESTARGS) $(TESTDIRS)
+	@ PATH=$(ToolDir):$(LLVM_SRC_ROOT)/test/Scripts:$$PATH $(PROJ_SRC_DIR)/../utils/test/MultiTestRunner.py $(TESTARGS) $(TESTDIRS) $(VGARG)
 
 clean::
 	@ rm -rf Output/