Merge pull request #28 from dcci/env

Don't assume python is in /usr/bin. Use 'env' instead.
diff --git a/build_script.py b/build_script.py
index 8262de1..fb4b6d4 100755
--- a/build_script.py
+++ b/build_script.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 # This source file is part of the Swift.org open source project
 #