audio/supercollider: prepare for Boost-1.89, do not link with stub Boost::system (+)
Get rid of overlinking on empty stub library Boost::system, it is header-only since boost-1.70
Backport of upstream commits from MR7116: https://github.com/supercollider/supercollider/pull/7116
https://github.com/timblechmann/nova-tt/commit/b497ec33a733c84d53e4295955d1033e0add7dae
https://github.com/supercollider/supercollider/commit/ee3ce7319fb61676454199cfa7023b804954d31a
With hat: office/boost