For GNU wrapped tools (gcc, groff, texinfo, etc) the current MKUPDATE logic
in Makefile.gnuhost appears to break on reinstalls.

Run build.sh -r -u and watch your build explode in groff as it's install rule
is assuming make install already ran but it doesn't actually on this pass. 

Everything else manages to reinstall correctly because normal depend rules 
depend on the installed files. But..for gnu wrapped tools it's just depending 
on .install_done which won't run if .build_done didn't change (which likely 
won't on a -r -u)

Unless someone objects/has a better solution I'd like to expunge the
.install_done
logic trying to get fancy w. MKUPDATE and just make it always run a make
install in Makefile.gnuhost. Otherwise we'll need to extract all installed
files
so they can be properly depended against.

-- 
James