devel/gnustep-make: Fix and modernize pkg-plist

Running "make check-plist" on gnustep-make results in plist errors:

===> Checking for items in STAGEDIR missing from pkg-plist
  Orphaned: GNUstep/System/Library/Makefiles/Master/deb.make
  Orphaned: GNUstep/System/Library/Makefiles/deb-equivs-control.template
  Orphaned: GNUstep/System/Makefiles

The latest was caused by a keyword typo (I think) and the first two were
just missing.  While here, modernize the whole thing.  No @exec keywords
are needed -- the post-install takes care of the symlink already.


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@372584 35697150-7ecd-e111-bb59-0022644237b5
Fix some leftovers in most xpi-* ports after r370932


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@372585 35697150-7ecd-e111-bb59-0022644237b5