[MacPorts] #59113: gcc: cannot find systems headers with Xcode 11

[MacPorts]

#59113: gcc: cannot find systems headers with Xcode 11
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  Reporter:  abyrvalk        |      Owner:  (none)
      Type:  defect          |     Status:  new
  Priority:  Normal          |  Milestone:
 Component:  ports           |    Version:
Resolution:                  |   Keywords:
      Port:  gcc7 gcc8 gcc9  |
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Comment (by kencu):

 Yes, jeremy sure knows his tricks -- isn't it interesting that Apple
 included the 10.14 SDK in the XCode 11 command line tools, but no in Xcode
 11?

 If they had left the 10.14 SDK in with Xcode 11, we would have had -- get
 ready for it -- NONE of this angst!

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Ticket URL: <https://trac.macports.org/ticket/59113#comment:23>
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