meson: don't compile git-pack-redundant(1) with breaking changes

meson: don't compile git-pack-redundant(1) with breaking changes

We continue to compile the git-pack-redundant(1) builtin with Meson when
breaking changes are enabled even though we ultimately don't expose this
command at all. This is mostly harmless, but given that the intent of
the build option is to be as close as possible to the state where the
breaking change has been fully implemented this isn't optimal either.

Improve the situation by not compiling the builtin when breaking changes
are enabled.

Based-on-patch-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>