port clean all fails on clutter if quartz in etc/macports/variants.conf

[gthb (Gunnlaugur Thor Briem)]

In going through ​http://trac.macports.org/wiki/Migration (prompted by the Mavericks upgrade, as you might expect), the sudo port clean all step failed for me when it got to a port named clutter, saying “error evaluating variants” because +x11 conflicts with +quartz.

Commenting out the (single) line of variant flags in etc/macports/variants.conf got me past this. But it seems unnecessarily brittle that the clean operation should fail because of the configured variant flags.