Tom Anderson authored Jul 11, 2018 and Behdad Esfahbod committed Jul 16, 2018

FcConfigRealFilename() follows symlinks, but the link may be relative to the
directory containing the link.  For example, on my system, I have this file:

/etc/fonts/conf.d/99-language-selector-zh.conf ->
    ../conf.avail/99-language-selector-zh.conf

Since /etc/fonts/conf.d is probably not in PATH, open()ing the file would fail.
This change makes FcConfigRealFilename() return the canonicalized filename
instead.  So for the example above, it would return:

/etc/fonts/conf.avail/99-language-selector-zh.conf

This was causing bad font rendering in Chromium [1] after the regression I
introduced in 7ad010e8.

[1] https://bugs.chromium.org/p/chromium/issues/detail?id=857511