Fixed sphinx-build to match makefile usage

--HG--
branch : distribute
extra : rebase_source : 049179f267bb721c43f0e9bdec1dbed1d13a73b1

release.py

@@ -64,6 +64,8 @@ def build_docs():
 	subprocess.check_call([
 		'sphinx-build',
 		'-b', 'html',
+		'-d', 'build/doctrees',
+		'.',
 		'build/html',
 		],
 		cwd='docs')