Get supported_archs from command line

[Ryan Schmidt]

I'd like to know a port's supported_archs from a command line script.

"port info" doesn't appear to have a flag to display it.

This Tcl script shows how to get the list of subports from a portfile:

https://trac.macports.org/browser/contrib/mp-buildbot/tools/subports.tcl

However it does this by using mportinfo, and it doesn't look like mportinfo contains information on the supported archs.

Any ideas?