Use "all-local" instead of all in Makefile.am.

Summary:
Redefining an Automake rule totally blows away anything Automake puts in place.
By using all-local instead of all, we can just add to the generated rule.

Reviewed By: marc

Test Plan: make


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665499 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/py/Makefile.am b/lib/py/Makefile.am
index a91d28c..99aa2ce 100644
--- a/lib/py/Makefile.am
+++ b/lib/py/Makefile.am
@@ -1,7 +1,7 @@
 DESTDIR ?= /
 EXTRA_DIST = setup.py src
 
-all:
+all-local:
 	$(PYTHON) setup.py build
 
 # We're ignoring prefix here because site-packages seems to be