I'm trying to reproduce a toolchain from source to the point of being
able to produce binary identical output from an tag of our sources.
The toolchain used to use 2.20, so that's what I was going for. I
wanted to know why 2.20 had been removed. I.e. was it an accident or
was there some serious flaw with it and it was recalled. In that
latter case I need to think about whether we really DO want to produce
binary identical output or rather get the benefit of not having the
flaw. (whatever that might be).