Superenv: determine_optflags should return a string

This is saved in HOMEBREW_OPTFLAGS and later mutated by
ENV.universal_binary, so if this returns nil the sub will fail.
uade: add new HEAD resource

bencode-tools isn't well-known or used enough to justify its own
formula at this point in time, but it's a dependency for the HEAD
version of UADE.
sbt: fix typo

Closes #28851.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
mpd 0.18.10

Closes #28853.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>