[Fontconfig] separate cache file from directories?

[Han-Wen Nienhuys]

Behdad Esfahbod wrote:
> I do not know the exact answer to your question, but the per-user
> ~/.fonts.cache-1 file is there for something along the same
> lines.
 >

Great. How do I get it to work, though?
I have

<cache>/Users/hanwen/src/maclily/BUILD/image/
   Applications/LilyPond.app//Contents/Resources/font-cache</cache>

(without linebreak, of course) in my fonts.conf, but running LilyPond 
(the FC application) doesn't create the font-cache file, and fc-cache says

   fc-cache: "/System/Library/Fonts": skipping, no write access

Am I missing something?

-- 
  Han-Wen Nienhuys - hanwen at xs4all.nl - http://www.xs4all.nl/~hanwen