fix build of other packages (e.g. py-scipy) in some cases (e.g. when
WRKOBJDIR has a trailing slash)

Index: numpy/distutils/command/build_src.py
--- numpy/distutils/command/build_src.py.orig
+++ numpy/distutils/command/build_src.py
@@ -366,6 +366,7 @@ class build_src(build_ext.build_ext):
             #    incl_dirs.append(self.build_src)
             build_dir = os.path.join(*([self.build_src]
                                        +name.split('.')[:-1]))
+        build_dir = os.path.normpath(build_dir)
         self.mkpath(build_dir)
 
         if self.verbose_cfg:
