[build2] Build system reorganization (heads-up to distribution packagers)

[Matthew Krupcale]

On Mon, Oct 7, 2019 at 11:10 AM Boris Kolpackov <boris at codesynthesis.com> wrote:
> If I remember correctly, it was something about the type not being
> trivial which resulted in different ABI rules.

Yes, that appears to be what is happening around 20 min mark with
`struct pair`: with the `= default` destructor, the type is trivial
when `First` and `Second` are trivial. In this case, there is no
destructor call, and the `pair` is passed in registers instead of on
the stack. I suppose this is the same as when I had `= default`
constructor in `struct s` which also becomes trivial.