mingw64 (and presumably mingw) fails on French-language Windows 10

This is the output of x86_64-w64-mingw32-gcc -print-search-dirs on a French-configured windows 10:

installés: /usr/lib/gcc/x86_64-w64-mingw32/5.4.0/
programmes : =/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/:/usr/lib/gcc/x86_64-w64-mingw32/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/:/usr/lib/gcc/x86_64-w64-mingw32/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/../../../../x86_64-w64-mingw32/bin/x86_64-w64-mingw32/5.4.0/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/../../../../x86_64-w64-mingw32/bin/
libraries : =/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/../../../../x86_64-w64-mingw32/lib/x86_64-w64-mingw32/5.4.0/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/../../../../x86_64-w64-mingw32/lib/../lib/:/usr/x86_64-w64-mingw32/sys-root/mingw/lib/x86_64-w64-mingw32/5.4.0/:/usr/x86_64-w64-mingw32/sys-root/mingw/lib/../lib/:/usr/lib/gcc/x86_64-w64-mingw32/5.4.0/../../../../x86_64-w64-mingw32/lib/:/usr/x86_64-w64-mingw32/sys-root/mingw/lib/

flexlink fails to parse it because of the space between libraries and :

I don't know who had the bright idea of localizing this part of gcc but it looks like you'll need to adapt.

Reproduce the issue with x86_64-w64-mingw32-gcc -print-search-dirs on French-configured Windows and inspect flexlink's parsing of that output. Done means flexlink accepts the localized labels, including the space before the colon, without failing.