[Fontconfig] fc-cache does not work with Cygwin

[Michael Garvin]

Hi, ok so I dug in deeper and it seems that fontconfig's method of file
locking isn't really compatibile with cygwin (or cygwin doesn't fully
emulate Linux).  

 

When font config tries to "hard link" tempory lock file, cygwin gives a
permission denied error.  I can replicate it by commenting out the unlink()
calls and then from the command line trying a 'link' from the mkstemp file
to some name.