Re-using bootstrap in the half-strap

[Christopher Allan Webber]

Hello,

A thought this morning... one challenge with Guile's 2.1 branch is it
takes a lonnnng time to bootstrap.  There are good reasons for this, and
Andy Wingo has documented them:

  http://wingolog.org/archives/2016/01/11/the-half-strap-self-hosting-and-guile

However, I can't help but wonder if we could reuse the initial
bootstrapped compiler.  What if we had an external package that
contained *just* the scheme interpreter used to bootstrap the rest of
the system?  We might not need to separate the codebase, but have this
be a separate make output.

If you could package *just* the bootstrapped compiler, if a user doesn't
feel like waiting through the whole bootstrap process, they could use
the existing bootstrap package, like:

  ./configure --with-bootstrap=/path/to/guile-bootstrap

and maybe we could have a guile-bootstrap package in guix, etc.  If you
want to do the whole bootstrap yourself in the Guile package, you could
do so, but it wouldn't be a requirement, assuming you had that separate
package...

Thoughts?  Useful?  Badly informed?
 - Chris