Possibly related thought - rather than hand curating sets of PKGPATH
checks, would something of the form
- 'set _BUILDING_COMPILER' when building the compiler
- Only set GCC_REQD if _BUILDING_COMPILER is unset
work?
I don't think so, because then we get different binaries for a package
depending on whether it was asked for normally or bootstrapped. That's
the central hard point, and it could lead to an entirely different
pkgsrc instance to build the bootstrap compiler. That seems like a lot
of CPU time, but I think it's not that much, and it's fairly clearly
sound.
The straw proposal says to encode essentially as Jason has done, but in
the package Makefiles, not another place, and to reduce dependencies.
However, that is a NetBSD-centric approach as the set above is huge,
compared to what one needs on NetBSD 7, where far more tools from base
are acceptable.
See
https://wiki.netbsd.org/pkgsrc/gcc/
for discussion (although note that I have received comments that I
haven't edited against).