Make scripts executable by python2.

Add #!/usr/bin/python2 and the executable permission bit to all scripts
where missing.

BUG=angleproject:2209

Change-Id: Ib33017c17e579c371b89bbfbdb7136b870027dc5
Reviewed-on: https://chromium-review.googlesource.com/862987
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>
diff --git a/scripts/run_code_generation.py b/scripts/run_code_generation.py
old mode 100644
new mode 100755
index c5e93e2..a0cded0
--- a/scripts/run_code_generation.py
+++ b/scripts/run_code_generation.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2
 #
 # Copyright 2017 The ANGLE Project Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -178,4 +178,4 @@
         args += ['git']
     args += ['cl', 'format']
     print('Calling git cl format')
-    subprocess.call(args)
\ No newline at end of file
+    subprocess.call(args)