Add fontconfig trigger

This wil regenerate the fontconfig caches, accounting for modifications in
the system font directories.

src/triggers/triggers.d/0100fontconfig-cache.trigger

@@ -0,0 +1,23 @@
+#!/bin/sh
+# Post-installation hook for the FontConfig cache -*- mode: sh -*-
+#
+# Written by Adrian Perez de Castro <aperez@igalia.com>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+if test -x "$(which fc-cache 2>/dev/null)"; then
+    exec fc-cache --system-only
+fi