[parrot/parrot] f38599: [docs] fix $< gnuism in docs makefile

[GitHub]

  Branch: refs/heads/smoke-me/bsdmake-gh1125
  Home:   https://github.com/parrot/parrot
  Commit: f38599d5b3df55dd3eaa30358fc432a5b7da6cb2
      https://github.com/parrot/parrot/commit/f38599d5b3df55dd3eaa30358fc432a5b7da6cb2
  Author: Reini Urban <rurban at cpanel.net>
  Date:   2014-11-10 (Mon, 10 Nov 2014)

  Changed paths:
    M config/gen/makefiles/docs.in

  Log Message:
  -----------
  [docs] fix $< gnuism in docs makefile

Fixes GH #1125