Backport 517206 | gerald | 2019-11-10 from lang/gcc10-devel, which already
landed in lang/gcc9-devel as r517355 | gerald | 2019-11-13.
Add a new option PLUGINS that enables GCC's plugin framework. This is off by default for now, but something to possibly make the default after a bit of settling. I plan to backport this to lang/gcc9-devel and then lang/gcc9.
Submitted by: David Carlier <devnexen@gmail.com>
Differential Revision: https://reviews.freebsd.org/D22292