[phobos] [D-Programming-Language/installer] f12fb3: use 7za (not 7z) command

[GitHub via phobos]

  Branch: refs/heads/master
  Home:   https://github.com/D-Programming-Language/installer
  Commit: f12fb3cf04b027db27ad9ec8767272400fb42b21
      https://github.com/D-Programming-Language/installer/commit/f12fb3cf04b027db27ad9ec8767272400fb42b21
  Author: Martin Nowak <code at dawg.eu>
  Date:   2016-01-18 (Mon, 18 Jan 2016)

  Changed paths:
    M create_dmd_release/common.d

  Log Message:
  -----------
  use 7za (not 7z) command