MFC r289360,r289361,r289378,r289430,r289605,r289676:

MFC r289360,r289361,r289378,r289430,r289605,r289676:

  r289360:
    Add temporary workaround for .MAKE being applied to _worldtmp, since
    r251750.
  r289361:
    Consider top-level targets to be .PHONY as bmake won't build them otherwise
    if a file with the same name is found in the directory.
  r289378:
    Mark sub-make targets as .MAKE and .PHONY to handle -n and always-build
    properly.
  r289430:
    Remove .MAKE from targets that do more than just run sub-makes, such as
    calling rm or mtree.
  r289605:
    Add missing .PHONY for parallel subdir target.
  r289676:
    Add some missing '+', .MAKE, and .PHONY modifiers.

git-svn-id: svn://svn.freebsd.org/base/stable/10@291777 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f