astro/openuniverse: fix build on FreeBSD 15-CURRENT

ftime() is now provided by libutil; link -lutil in addition to -lcompat
to get it; this is harmless on older FreeBSD.

While we are at it, define LICENSE and fix USE_GL stage-qa warnings.

MFH: 2024Q4
(cherry picked from commit c3dde4ea970725e330129e79b3130457f08a1459)