Use OS-dependent directory separator - a / on windows is interpreted by LINK...

Use OS-dependent directory separator - a / on windows is interpreted by LINK as a command line switch

--HG--
extra : transplant_source : %A8%F23%AF%26%BC%82y1%86S%1Ac%D3%40%089o%DCQ

pyximport/pyximport.py

@@ -497,7 +497,7 @@ def install(pyximport=True, pyimport=False, build_dir=None, build_in_temp=True,
     runtime for .py files and Py2 for .pyx files.
     """
     if not build_dir:
-        build_dir = os.path.expanduser('~/.pyxbld')
+        build_dir = os.path.join(os.path.expanduser('~'), '.pyxbld')
         
     global pyxargs
     pyxargs = PyxArgs()  #$pycheck_no