[Fontconfig] Fontconfig cache file update fails on Windows (also Cygwin)

[Masamichi Hosoda]

Hello,

I've found an issue of fontconfig on Windows.
If you have an old cache file and need updating,
the updating fails on Windows (both MinGW and Cygwin).

I've created a patch and reported it to Bugzilla.
https://bugs.freedesktop.org/show_bug.cgi?id=99360

Thanks