/usr/include/ is in libmusicbrainz3-dev 3.0.2-2.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/musicbrainz3/
/usr/include/musicbrainz3/model.h
/usr/include/musicbrainz3/mbxmlparser.h
/usr/include/musicbrainz3/defines.h
/usr/include/musicbrainz3/factory.h
/usr/include/musicbrainz3/release.h
/usr/include/musicbrainz3/iwebservice.h
/usr/include/musicbrainz3/user.h
/usr/include/musicbrainz3/disc.h
/usr/include/musicbrainz3/utils.h
/usr/include/musicbrainz3/results.h
/usr/include/musicbrainz3/musicbrainz.h
/usr/include/musicbrainz3/labelalias.h
/usr/include/musicbrainz3/query.h
/usr/include/musicbrainz3/metadata.h
/usr/include/musicbrainz3/includes.h
/usr/include/musicbrainz3/artistalias.h
/usr/include/musicbrainz3/filters.h
/usr/include/musicbrainz3/mb_c.h
/usr/include/musicbrainz3/tag.h
/usr/include/musicbrainz3/label.h
/usr/include/musicbrainz3/relation.h
/usr/include/musicbrainz3/track.h
/usr/include/musicbrainz3/artist.h
/usr/include/musicbrainz3/entity.h
/usr/include/musicbrainz3/lists.h
/usr/include/musicbrainz3/webservice.h
/usr/include/musicbrainz3/releaseevent.h