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

[Masamichi Hosoda]

>>> It is better that there is a possibility of success rather than a
>>> way that does not succeed at all, in my humble opinion.
>> 
>> Exactly.
> 
> I'd like my patch to be merged.
> 
> This issue is very major and serious to use fontconfig on Windows.

On Windows (MinGW), fontconfig 2.12.3 still fails to update the font cache.

The patch proposed here
https://bugs.freedesktop.org/show_bug.cgi?id=99360
can solve it.