up by pk (and fix comments to match):
* A .WAIT here means that only the *immediately preceding* target needs
to be added to the list of "install-foo" targets used to ensure that
dependencies are installed (otherwise much more than is necessary
gets installed during the build process, increasing build time here)
* If building only an individual target such as "dependall-yacc", the
prerequisites may need to be built before running their "install-foo"
targets -- so add a dependency in that case on "dependall-foo".
a45d07b1e5