Build warning on win32: unrecognized option '/mwindows'; ignored

It looks like I've successfully built the latest MPL svn (rev 3273) with
the latest WxPython in Python 2.5.1 on win32 using MSVC 7.1.
Lots of (what I take it aren't important) type conversion warnings
came up, but this warning stood out:

building 'matplotlib._windowing' extension
C:\bin\Microsoft Visual Studio .NET 2003\Vc7\bin\cl.exe /c /nologo /Ox /MD /W3 /GX /DNDEBUG -IC:/include -IC:\bin\Python25\include -IC:\bin\Python25\PC /Tpsrc/_windowing.cpp /Fobuild\temp.win32-2.5\Release\src/_windowing.obj
C:\bin\Microsoft Visual Studio .NET 2003\Vc7\bin\link.exe /DLL /nologo /INCREMENTAL:NO /LIBPATH:C:/lib /LIBPATH:C:\bin\Python25\libs /LIBPATH:C:\bin\Python25\PCBuild user32.lib /EXPORT:init_windowing build\temp.win32-2.5 \Release\src/_windowing.obj /OUT:lib\matplotlib\_windowing.pyd /IMPLIB:build\temp.win32-2.5\Release\src\_windowing.lib -mwindows
LINK : warning LNK4044: unrecognized option '/mwindows'; ignored
    Creating library build\temp.win32-2.5\Release\src\_windowing.lib and object build\temp.win32-2.5\Release\src\_windowing.exp

Is this important? MPL seems to work fine. I compiled using:

python build_ext --inplace --force

I've got the win32_static folder in my MPL root, extracted from, and I've
overwritten all the wxPython lib and header files there with those in
the latest wxPython2.8-win32-devel-