dbusmenu-qt5 build failure on 10.7 and 10.8 buildbots because of using libstdc++

[Ryan Schmidt]

> On Oct 6, 2016, at 7:40 AM, René J.V. Bertin <rjvbertin at gmail.com> wrote:
> 
>> We want to move the matter of determining that an error condition exists
>> from the portfiles and portgroups to MacPorts base. Then it will be easier
>> for the buildbot to query MacPorts base and ask if the port will be
>> installable, and skip it if not
> 
> I think we're not exactly thinking about the same things. I don't think you can expect ports to know that without being able to include the PortGroups they require. So even if the fundamental mechanism is part of the base layer the error could still be determined in a PortGroup. And I think it'd make sense if the cxx11 portgroup raised the "don't build" signal if it detects a host that doesn't have libc++ installed.

I've explained the matter as best I can. You can refer to the mailing list archives for more details, specifically Clemens' explanation for why the matter must be handled by MacPorts base, not ports.