Can a makefile have a directory as a target?

Your makefile should do what you expect. Since yank has no dependency, it won't be remade if it exists. So this looks like a bug in makepp. You could confirm this by trying your makefile with a traditional implementation of make.

In a makefile, is a directory name a phony target or "real" target?

What you need is an order-only prerequisite.

A quick search didn't turn up any reference for makepp and order-only prerequisites, but it may still work.

Yes, a Makefile can have a directory as target.

Your problem could be that the cd doesn't do what you want: it does cd and the git clone is carried out in the original directory (the one you cded from, not the one you cded to). This is because for every command in the Makefile an extra shell is created. A workaround is to run cd and clone as one command with the shell's &&.

This should work:

bla/f: dir
    cd dir && touch f

dir:
    mkdir dir