> Suppose we had a list of "rebuild tools" -- 
>      make, /usr/src/share/mk/*,  gcc,  as, ar, ranlib, nm, tsort,
>      lorder, sort, join, lex, yacc, rpcgen,  lint, 
> 
> plus others, and rules to build the latest source on your old system,
> put them in a sandbox, and clean up the source tree, before doing
> `make build'.  And a way to use that sandbox as a "cross-compilation
> system".  And if building the "sandbox" contents fails (due to
> dependencies between the sandbox contents) , you get to repair things
> manually, as you do now.  How far would that go to solving your problem?

The stuff in your sandbox should build on *any* Unix system.  Tool X 
shouldn't contain any dependencies on itself or any tools that require X 
to already exist before they can be built: mathematically, the 
dependencies should be a directed acyclic graph.

I note in passing here that there are a whole bunch of GNU tools in 
existence that are supposed to help with all this (autoconf, automake 
etc).  It seems a pity that we can't use them.

Richard.