When writing a file with write_file() we have to inform the pro file parser
cache to discard the file if it's existant in the cache, to ensure that
calling include() after write_file() always works.
Change-Id: I7d09269a57de55ca30b0e11dd40770de9f919f64
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
