[phobos] [D-Programming-Language/installer] 6f21b1: skip building installer when docs are skipped

[GitHub via phobos]

  Branch: refs/heads/master
  Home:   https://github.com/D-Programming-Language/installer
  Commit: 6f21b12cecffbbaa4915b1466df99d8624e2c061
      https://github.com/D-Programming-Language/installer/commit/6f21b12cecffbbaa4915b1466df99d8624e2c061
  Author: Martin Nowak <code at dawg.eu>
  Date:   2015-02-18 (Wed, 18 Feb 2015)

  Changed paths:
    M create_dmd_release/build_all.d

  Log Message:
  -----------
  skip building installer when docs are skipped