elegant ways to build a package two times

[md@Linux.IT (Marco d'Itri)]

The inn2 packages is not as useful as it should be, since it does not
support LFS which is mandatory for large servers. I cannot just enable
LFS support since there is no transition path for some classes of users,
so we need both inn2 and inn2-lfs packages.

I am looking for *elegant* ways to build both packages from the same
source with the least possible duplication of the code in debian/rules
and of the debian/ debhelper files (the package is complex and needs
much work before and after make install).
Please let me know if you know about packages which solved similar
issues.

INN uses autoconf but not automake, so mkdir bin && ./configure does
not generate working makefiles.

-- 
ciao,
Marco