Oh, another thing: if I switch target architecture, build.sh rebuilds a
lot of tools from TOOLDIR/bin, things like nbmakefs, nbrpcgen and
nbyacc.  That seems unneeded?

It seems that it may come from the fact that the tools' objects are
stored in OBJDIR/tools, which necessarily must differ per target arch.
Perhaps an way can be found to share these directories?

-Olaf.
-- 
___ Olaf 'Rhialto' Seibert      -- You author it, and I'll reader it.
\X/ rhialto/at/xs4all.nl        -- Cetero censeo "authored" delendum esse.