[RFC] generate maybe dependencies from the template

[Nathanael Nerode]

Paolo Bonzini wrote:
> This patch is a proposal for an alternative way to create maybe 
> dependencies.

Basically I like the concept.

What I *don't* like is the fact that this requires multiple 
carefully-timed sed passes over the top level Makefile, which will 
probably turn out to be very hard to maintain later.

Thoughts?

> The advantages are a 30% (or more, e.g. if you're over NFS) speedup in 
> config.status, removing the knowledge of makefile targets from the 
> configure script, and setting up a framework which will also be used 
> when a toplevel configure switch will enable toplevel bootstrapping.
> 
> There is a small behavioral change, in that a hard dependency on 
> "all-TARGET" when the target is not available will cause make to abort, 
> instead of trying and failing to execute the target