Go 1.20 and bootstrapping

[Benny Siegert <bsiegert%gmail.com@localhost>]

Hi!

Go 1.20 will require Go 1.17.13 or newer for bootstrapping.

We have two options:

1. Depend on go118 and use that for bootstrapping. Go 1.17 had a few
issues on NetBSD, so 1.18 is a better choice. This means that
installing Go 1.20 from scratch will first build go14 (which is in C),
then go118, then go120.

2. Use go-bin for bootstrapping -- apart from the fact that the
aarch64 version is too old. The concern, of course, is that you have
to be confident in a binary bootstrap kit.

Should we offer both possibilities? Which one should be the default?

-- 
Benny