Personally I'd say we have better things to work on than maintaining
multiple buildsystems for notmuch. Or than resolving possible packaging
bugs originating in the use of different buildsystems.

GNU has a very wide install bas, it's has a low footprint,  and it
happened to be the choice of the initial developers. All of this makes
it the best choice imo.

While I don't want to start a discussion on the merits of various
buildsystems, I'll mention that, in my role as a packager, I'd choose
just about anything over scons.

My 2 cents,
Ingmar

-- 
Exherbo KDE, X.org maintainer