[MacPorts] #62847: opencv4: fix build failures for MacOS 10.7 and 10.8

[MacPorts]

#62847: opencv4: fix build failures for MacOS 10.7 and 10.8
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  Reporter:  mascguy  |      Owner:  mascguy
      Type:  defect   |     Status:  assigned
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:
      Port:  opencv4  |
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Comment (by mascguy):

 Full log attached, for our MacOS 10.8 buildbot. Though the error is the
 same for 10.7.

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Ticket URL: <https://trac.macports.org/ticket/62847#comment:1>
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