Do not remove UUID file when a scanned directory is empty
Because FcDirCacheDeleteUUID does not reset the modification time on the directory, and because FcDirCacheRead unconditionally creates the UUID file each time it is run, any empty directory in the cache will get its timestamp changed each time the cache for that directory is read.
Instead, just leave the UUID file around as it is harmless.
The alternative would be to only create the UUID file after the cache has been created and the directory has been discovered to be non-empty, but that would delay the creation of the UUID file.
Signed-off-by: Keith Packard email@example.com