Fixes extensions build.

Author: sdispater

setup.py

@@ -35,7 +35,7 @@ def get_version():
 if with_extensions == '1' or with_extensions is None:
     with_extensions = True
 
-if hasattr(sys, 'pypy_version_info'):
+if with_extensions == '0' or hasattr(sys, 'pypy_version_info'):
     with_extensions = False
 
 extensions = []
@@ -46,7 +46,6 @@ def get_version():
                   extra_compile_args=['-Wno-unused-function']),
     ]
 
-
 class BuildFailed(Exception):
 
     pass