macports.tcl: Remove unnecessary shell invocation.
macports.tcl: Remove unnecessary shell invocation.

The "system" proc already runs a new shell.
https://lists.macosforge.org/pipermail/macports-dev/2014-August/027658.html.

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@123792 d073be05-634f-4543-b044-5fe20cf6d1d6

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