Bug#846976: colobot: oggenc-reproducibly.patch is a no-op

[Clint Adams]

Source: colobot
Version: 0.1.9-3
User: reproducible-builds at lists.alioth.debian.org
Usertags: randomness

The `--serial "${FILENAME}"` introduced by oggenc-reproducibly.patch
does not have the desired effect, because since "${FILENAME}" does
not expand to a number, oggenc still generates a random serial number.

Perhaps ${FILENAEME} can be hashed into an integer somehow.