[MacPorts] #59243: clang-9.0 dependency error in macOS 10.15

[MacPorts]

#59243: clang-9.0 dependency error in macOS 10.15
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  Reporter:  jerryzj    |      Owner:  jeremyhu
      Type:  defect     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.6.1
Resolution:             |   Keywords:
      Port:  clang-9.0  |
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Comment (by kencu):

 reproducible builds. It's a very valid concept we try aim for.

 MacPorts can't know what cmake you have, or how it's exactly installed and
 configured, unless we use ours.

 Same for all the other tools.

 But for new os versions with current Xcodes, we might need to make an
 exception for cctools and ld64...

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Ticket URL: <https://trac.macports.org/ticket/59243#comment:7>
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