Add %check_clang_tidy and %clang_tidy_diff.

With this, site specific lit configs can inject parameters into the
test scripts if they need site specific parameters.

Next up: enable check_clang_tidy to take a resource dir to enable
non-standard locations for builtin includes.

llvm-svn: 251010
diff --git a/clang-tools-extra/test/clang-tidy/modernize-make-unique.cpp b/clang-tools-extra/test/clang-tidy/modernize-make-unique.cpp
index ce92b4c..fdf834e 100644
--- a/clang-tools-extra/test/clang-tidy/modernize-make-unique.cpp
+++ b/clang-tools-extra/test/clang-tidy/modernize-make-unique.cpp
@@ -1,4 +1,4 @@
-// RUN: %python %S/check_clang_tidy.py %s modernize-make-unique %t
+// RUN: %check_clang_tidy %s modernize-make-unique %t
 
 namespace std {