[MacPorts] #58442: gcc9 (and other gccN) fails to install on Mojave, Xcode-10.2.1

[MacPorts]

#58442: gcc9 (and other gccN) fails to install on Mojave, Xcode-10.2.1
-------------------------+--------------------
  Reporter:  mouse07410  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:
      Port:  gcc9        |
-------------------------+--------------------

Comment (by cjones051073):

 'Doctor, doctor, it hurts when I do this' 'Then don't do that!'

 Seriously... You are using a non-standard variant which counts as a
 special build. Please just as a test try reinstalling with the standard
 default options and see if that fixes the errors. Even if you need the
 assertions, you will then know enabling them is causes you the problems
 and you can go from there...

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Ticket URL: <https://trac.macports.org/ticket/58442#comment:36>
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