[MacPorts] #58776: macOS 10.15 libgcc9 fails to build with Xcode 11

[MacPorts]

#58776: macOS 10.15 libgcc9 fails to build with Xcode 11
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  Reporter:  vdoublie  |      Owner:  (none)
      Type:  defect    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:
Resolution:            |   Keywords:  catalina
      Port:  libgcc9   |
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Comment (by AP1010):

 This doesn't seem to make too much sense, but in my case the following
 happened:
 I had Catalina + Xcode 11.1 + command line tools installed. The CLT were
 installed by using xcode-xelect --install. The port would not build.

 I downloaded the stand-alone CLT package from  Apple. Installed it on top
 of what I already had, and....
 The port built successfulyy.

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Ticket URL: <https://trac.macports.org/ticket/58776#comment:17>
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