SCons build tool speed

[Peter Hansen]

knight at baldmt.com wrote:
> You're right that build times are dominated by the external commands
> when rebuilds occur.  If nothing needs to be rebuilt, though, the
> wall-clock time is obviously dominated by how long it takes for
> the build tool to decide that.  A build tool that doesn't decide
> whether or not targets are up-to-date *and* dispatch the commnds
> to rebuild them reasonably quickly and efficiently doesn't do a
> good job of serving its users.

That answer, combined with Mike's response pointing out
that tools more sophisticated than basic "make" actually
can delve into the source and identify the dependencies,
removes my confusion.  Thanks. :)

-Peter