netbsd-9 and pkgsrc-2022Q3 (libunwind and GCC 10)

["John D. Baker" <jdbaker%consolidated.net@localhost>]

As "lang/libunwind" in pkgsrc-HEAD (and thus the next quarterly branch)
now requires GCC 10 or later to build, I'm pondering the way forward for
netbsd-9.

Particularly, since my preferred set of packages requires pkgsrc GCC
(gcc7) anyway in order to get 'gfortran', I'd rather not have to build
multiple versions of GCC (especially as package sizes are starting to
cramp my filesystems).  Also, I seem to recall that it's generally not
a good idea to link things built with different versions of GCC (at least
C++ objects).

If I want to use GCC 10 to build all of my packages, should I build
it first, then put a global "GCC_REQD+=10" in "/etc/mk.conf", and then
proceed to update the rest of my packages?  Am I likely to run into
a circular dependency and if so, how to avoid it?

Thanks for any pointers and tips.

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