[build2] -s switch

[Boris Kolpackov]

Moldmann Max (DC-MH/ENG52-NA) <Max.Moldmann at boschrexroth-us.com> writes:

> The -s switch is perfect to quickly see the first compilation problem.
> But as it only uses a single core the target update operation takes a
> long time compared to a normal multicore build. Thus the idea to maybe
> have the target update operations run in parallel, but then switch back
> to single core for the actual compilation. 

Ok, firstly, what you call "target update" is called "match phase" and
"actual compilation" -- "execute phase".

While theoretically we could run the match phase in parallel and execute
serially, I don't think it will (always) do what you want: imagine you
have 100 source files that need recompilation and the error is in the
last one. In your proposed mode you will end up waiting on serial
compilation of 99 files before seeing the error.

Boris