[MacPorts] #54948: optipng 0.7.6 fails to build on MacOS 10.13

[MacPorts]

#54948: optipng 0.7.6 fails to build on MacOS 10.13
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  Reporter:  fracai   |      Owner:
      Type:  defect   |     Status:  new
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:  10.13 highsierra
      Port:  optipng  |
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Changes (by fracai):

 * Attachment "main.log" added.

 build log

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Ticket URL: <https://trac.macports.org/ticket/54948>
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