[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):

 I think  cctools is calling it in.

 You can find out with {{{port rdeps clang-9.0}}}

 We should not be making people install cctools or ld64 on Catalina (or
 Mojave or High Sierra).  If we do ask them to install it, then it should
 be the {{{+xcode}}} variant of them, which is a no-op. I have to talk to
 Jeremy about this at some point

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Ticket URL: <https://trac.macports.org/ticket/59243#comment:3>
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