[MacPorts] #69173: port fails to upgrade to 2.9.0

[MacPorts]

#69173: port fails to upgrade to 2.9.0
-------------------------+--------------------
  Reporter:  mouse07410  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  base        |    Version:  2.9.0
Resolution:              |   Keywords:
      Port:              |
-------------------------+--------------------

Comment (by kencu):

 generally speaking, trying to outsmart xcrun by setting the SDKROOT
 yourself (as some folks are wont to do in their terminal startup scripts,
 or manually), or, God forbid, making your own symlinks in the SDK folder
 between the SDKs to match what you imagine might be a good plan, is going
 to be a doomed enterprise that will cause nothing but build failures,
 troubles, and hassles.

-- 
Ticket URL: <https://trac.macports.org/ticket/69173#comment:5>
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