Add a parallel compilation fix for fontconfig

This patch adds a patch to fix bug
https://bugs.freedesktop.org/show_bug.cgi?id=16464 affecting parallel
compilation of fontconfig.

The patch is the one proposed in the bugzilla entry, available at
https://bugs.freedesktop.org/attachment.cgi?id=17294

.

Without this patch, the compilation (at BR2_JLEVEL > 1) of fontconfig
sometimes fails with:

In file included from fc-case.c:25:
../src/fcint.h:118:21: error: fcalias.h: No such file or directory

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>