fontcache: allow to pass extra parameters and environment to fc-cache

* this can be useful for passing extra parameters, pass
  -v by default to see what's going on in do_rootfs
* we need to use this for extra parameter we implemented
  in fontconfig:
  --ignore-mtime always use cache file regardless of font directory mtime
  because the checksum of fontcache generated in do_rootfs
  doesn't match with /usr/share/fonts directory as seen on
  target device causing fontconfig to re-create the cache
  when fontconfig is used for first time or worse create
  new cache in every user's home directory when /usr/
  filesystem is read only and cache cannot be updated.

  Running FC_DEBUG=16 fc-cache -v on such device shows:
  FcCacheTimeValid dir "/usr/share/fonts" cache checksum 1441207803 dir checksum 1441206149
* my guess is that the checksum is different, because pseudo
  (which is unloaded when running qemuwrapper) or because some
  influence of running the rootfs under qemu.

(From OE-Core rev: 22bb7e11f9c75943efa07997a98304aa01d14699)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joshua Lock <joshua.lock@collabora.co.uk>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/postinst-intercepts/update_font_cache

@@ -1,5 +1,5 @@
 #!/bin/sh
 
-PSEUDO_UNLOAD=1 qemuwrapper -L $D -E LD_LIBRARY_PATH=$D/${libdir}:$D/${base_libdir}\
-					$D${bindir}/fc-cache --sysroot=$D
+PSEUDO_UNLOAD=1 qemuwrapper -L $D -E LD_LIBRARY_PATH=$D/${libdir}:$D/${base_libdir} \
+					-E ${fontconfigcacheenv} $D${bindir}/fc-cache --sysroot=$D ${fontconfigcacheparams}
 chown -R root:root $D${fontconfigcachedir}