build gcc with distcc

[Ben Elliston]

> On a somewhat related note, I'd be interested to hear if ccache
> could be snuck into bootstrapping to speed up recompiles in the
> intermediate stages, especially with incremental changes.  (Anyone
> tried this?)  I've noted that ccache-ing only speeds up the first
> stage, as one would expect.

> There might be a subtle issue with ccache assuming that the compiler
> that created a cache-hit object did not change.  I'm only aware of
> ccache verifying compiler versions (string compare) in the
> hit-check, which alone doesn't suffice to guarantee that the cache
> is (or should be) hit.

No, it records the timestamp of the compiler driver.  These would
always be different in a bootstrap run, so you would never get any
cache hits for second and third stage object files.

Ben