setup: integrate osutil C extension into extmodules initialization

setup.py

@@ -503,12 +503,11 b' extmodules = ['
                                     'mercurial/parsers.c',
                                     'mercurial/pathencode.c'],
               depends=common_depends),
+    Extension('mercurial.osutil', ['mercurial/osutil.c'],
+              extra_link_args=osutil_ldflags,
+              depends=common_depends),
     ]
 
-extmodules.append(Extension('mercurial.osutil', ['mercurial/osutil.c'],
-                            extra_link_args=osutil_ldflags,
-                            depends=common_depends))
-
 try:
     from distutils import cygwinccompiler