[MacPorts] #55709: libcxx @5.0.1_1 build fails with gcc

[MacPorts]

#55709: libcxx @5.0.1_1 build fails with gcc
---------------------+-------------------------------
  Reporter:  potmj   |      Owner:  jeremyhu
      Type:  defect  |     Status:  assigned
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:  2.4.2
Resolution:          |   Keywords:  leopard universal
      Port:  libcxx  |
---------------------+-------------------------------

Comment (by kencu):

 All `macports.conf` are set up with a default `universal_archs`. Even if
 one is not specifically added to `macports.conf` there is already a
 default for that setting in base. That setting does not force everything
 to build universal. It only says what universal would be, if universal is
 called.

 And on a 10.5 Intel machine, universal should not include `ppc` if you're
 following [wiki:LibcxxOnOlderSystems] unless you are prepared for the
 ramifications of that. Actually, if that is not in the instructions, I
 should add it to them.

 Perhaps you are thinking about +universal in your default variants.
 '''That''' would make everything build universal.

 Re: cmake --  I also have a personal cmake39 port
 <https://github.com/kencu/myports/tree/master/devel/cmake39> that doesn't
 require c++11 as well, but MacPorts has decided not to do that to keep
 things coherent and maintainable, and Ryan spent the better part of a week
 working on cmake to make sure it could bootstrap the current version of
 cmake on all systems (except 10.4, which doesn't build the current cmake).

--
Ticket URL: <https://trac.macports.org/ticket/55709#comment:9>
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