Check to see if a variant exists for a specific port before trying to use it.  This should fix a lot of dependency issues now that variants are tracked in the registry, and should avoid rebuilding ports multiple times with non-existent variants in order to satisfy dependencies.
Check to see if a variant exists for a specific port before trying to use it.  This should fix a lot of dependency issues now that variants are tracked in the registry, and should avoid rebuilding ports multiple times with non-existent variants in order to satisfy dependencies.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@7714 d073be05-634f-4543-b044-5fe20cf6d1d6

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