%-rules are a gmakeism, and similarly, it appears that GNU and BSD
make treat $< differently for target rules.  This commit should
hopefully make BSD make happier when it comes to make dist.


git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5485 d4fa192b-c00b-0410-8231-f00ffab90ce4