clover/il: return IL only for spirv and correct length

This is specified as  char[] and I don't think requires null termination,
Also we should only return IL based programs.

Fixes CTS spirv_new get_program_il

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11868>
1 file changed