[MacPorts] #55410: gcc7 @7.2.0 does not build on Mac OS X 10.6.8, Snow Leopard, because of "Undefined symbols for architecture x86_64"

[MacPorts]

#55410: gcc7 @7.2.0 does not build on Mac OS X 10.6.8, Snow Leopard, because of
"Undefined symbols for architecture x86_64"
------------------------+-------------------------
  Reporter:  ballapete  |      Owner:
      Type:  defect     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.4.2
Resolution:             |   Keywords:  snowleopard
      Port:  gcc7       |
------------------------+-------------------------

Comment (by kencu):

 Is this system configured to libc++ with LibcxxOnOlderSystems?

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Ticket URL: <https://trac.macports.org/ticket/55410#comment:1>
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