[MacPorts] #54949: gcc5 @5.4.0_2 fails to build on macOS 10.13

[MacPorts]

#54949: gcc5 @5.4.0_2 fails to build on macOS 10.13
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  Reporter:  matteopuel  |      Owner:
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:  highsierra
      Port:  gcc5        |
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Comment (by raimue):

 Please attach a [https://guide.macports.org/#development.patches.portfile
 unified diff] instead of full a Portfile. That makes it easier to see what
 you actually changed. Also, please do not leave commented lines without
 explanation in the Portfile and avoid to make unnecessary changes. Note
 you cannot remove `epoch`, it needs to stay forever.

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Ticket URL: <https://trac.macports.org/ticket/54949#comment:9>
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