libgl-gdi: Mingw-w64 in 32bit mode matches the Mingw32's .DEF semantics.

src/gallium/targets/libgl-gdi/SConscript

@@ -27,7 +27,7 @@ if env['llvm']:
     env.Append(CPPDEFINES = 'HAVE_LLVMPIPE')
     drivers += [llvmpipe]
 
-if env['gcc'] and 'w64' not in env['CC'].split('-'):
+if env['gcc'] and env['machine'] != 'x86_64':
     # DEF parser in certain versions of MinGW is busted, as does not behave as
     # MSVC.  mingw-w64 works fine.
     sources += ['#src/gallium/state_trackers/wgl/opengl32.mingw.def']