[libc++] Make executor scripts executable

This allows running the scripts directly, without running them through
Python.
diff --git a/libcxx/utils/ssh.py b/libcxx/utils/ssh.py
old mode 100644
new mode 100755
index 314b13b..f74ed78
--- a/libcxx/utils/ssh.py
+++ b/libcxx/utils/ssh.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 #===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.