For those of you who don't know, check-reqs is an eclass that is
occasionally used by a few packages that have ludicrously high build
requirements. Typical examples have included anything using Haskell (the
programming language with built-in memory leaks!) and certain C++
template metaprogamming voodoo.

Currently it just exports a single function that will warn (or die,
based upon user preference) if the build requirements aren't met. There
has been a request for a clean way of handling packages that can be
built in two different ways that give the same end result (typical
example is use of a really slow but low memory requiring algorithm vs a
fast but memory intensive algorithm when building data tables).

How does something like the attached look? (Yes, it's using old-school
[ rather than [[, since the rest of the eclass is written that way. I
might switch the whole thing over at some point.)

-- 
Ciaran McCreesh : Gentoo Developer (Wearer of the shiny hat)
Mail            : ciaranm at gentoo.org
Web             : http://dev.gentoo.org/~ciaranm