[clang-tidy] Use a python script instead of a shell script to run clang-tidy tests.

Summary:
Add check_clang_tidy.py script that is functionally identical to the
check_clang_tidy.py, but should also be functional on windows.

I've verified that the script works on linux. Would be nice if folks using
Windows could test the patch before I break windows bots ;)

Reviewers: chapuni, aaron.ballman

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D12180

llvm-svn: 245583
diff --git a/clang-tools-extra/test/clang-tidy/google-readability-todo.cpp b/clang-tools-extra/test/clang-tidy/google-readability-todo.cpp
index 9f4e3a8..d2e3b6c 100644
--- a/clang-tools-extra/test/clang-tidy/google-readability-todo.cpp
+++ b/clang-tools-extra/test/clang-tidy/google-readability-todo.cpp
@@ -1,5 +1,4 @@
-// RUN: $(dirname %s)/check_clang_tidy.sh %s google-readability-todo %t -config="{User: 'some user'}" --
-// REQUIRES: shell
+// RUN: %python %S/check_clang_tidy.py %s google-readability-todo %t -config="{User: 'some user'}" --
 
 //   TODOfix this1
 // CHECK-MESSAGES: [[@LINE-1]]:1: warning: missing username/bug in TODO