util: Makefile.sources: Add disk_cache_os.{c,h}

The functions in disk_cache_os are referenced by disk_cache but these
files are not included in builds based on Makefile.sources such as
Android, resulting in linker errors.

Fixes: 4339ecde35c ("disk_cache: move cache dir generation into OS specific helper file")
Signed-off-by: Marijn Suijten <marijns95@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6702>
1 file changed