Support for building +quartz

[Mojca Miklavec]

Hi,

This is a reminder about one burning issue.

I'm currently trying to build wine and I don't see any way to avoid
building gtk3 from sources (gtk3 seems to build forever). Also, I
would like to have gtk3 +quartz build anyway which means compiling
from source on a no-matter-what basis.

Could we push support for variants further?
    https://trac.macports.org/ticket/52742

Sure, we could automate this, but at least having the ability to
manually trigger some more complex builds (in particular in the
+universal area for wine) would really help.

Thank you,
    Mojca