audio/p5-Ogg-Vorbis-Header: unbreak the port's build against Clang 16
write_vorbis() must return an integer, but was returning &PL_sv_undef
in several places vs. zero in other error paths. Follow the original*
implementation and replace those with zeros as well.
To make hunting potential compiler-related bugs easier in the future,
respect ${CC} and mute one harmless but particularly annoying warning
which clutters the build log way more than does any good.