I updated the wiki page:
https://wiki.netbsd.org/pkgsrc/gcc/
The tl;dr is that I would like to head for
reduce dependencies of gcc when it doesn't hurt (specifically, enable
gcc-inplace-math by default on 4.8 and 4.9), even if this won't help a
lot.
allow C/C++ versions to differ, realizing that this may be a bad idea,
in which case we won't.
choose gcc5 as the C++ version for netbsd-7, because 4.8 is too old.
Don't use a separate prefix for the bootstrap compiler, and pass a "we
are bootstrapping" variable recursively, and omit compiler selection
logic. Take a don't-worry-be-happy approach to consistency issues
from that, and deal with them if they are troublesome.
I think we have a volunteer to produce a patch. Please have a look at
the wiki page and either weigh in on listed alternatives or suggest new
ones if you think it's broken.
I really want to get this in during Q1; now even NetBSD 7 is having
trouble.