base: Fix parallel build (https://trac.macports.org/ticket/20378).
base: Fix parallel build (https://trac.macports.org/ticket/20378).

Problem was that pkg_mkIndex was getting run before the dylibs were
built.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@54781 d073be05-634f-4543-b044-5fe20cf6d1d6

neverpanic/macports-base,danchr/macports-base,danchr/macports-base,macports/macports-base,neverpanic/macports-base,macports/macports-base