A parallel 'debian/rules build' will now invoke 'debian/rules.real
build' twice in parallel, which is disastrous.
- Add and use proper build-arch and build-indep targets in
debian/rules.gen and debian/rules.real
- Assign a separate temporary directory to each target in
debian/rules.real. Add the directories to .gitignore and
the clean rule.
- Pull installation of the lockdep wrapper (which is indep)
up into debian/rules.real so that we don't end up building
liblockdep twice in parallel.