[MacPorts] #59094: Error after updating XCode to 11.0

[MacPorts]

#59094: Error after updating XCode to 11.0
-----------------------+--------------------
  Reporter:  eisGeist  |      Owner:  (none)
      Type:  defect    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:  2.6.0
Resolution:            |   Keywords:
      Port:            |
-----------------------+--------------------

Comment (by kencu):

 You are running into a problem we are dealing with all over MacPorts right
 now:
 {{{
 :info:build clang: warning: no such sysroot directory:
 '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk'
 [-Wmissing-sysroot]
 }}}
 We have found we have baked the `MacOSX10.14.sdk` into build files all
 over the place, and now that SDK is gone (replaced by `MacOSX10.15.sdk`).

 If you are really eager to get going, this workaround will most likely
 work out [ticket:59113#comment:14]. It would not appear to be able to do
 any harm at all.

 If you can wait, there are various potential fixes making their way
 through the vetting process.

-- 
Ticket URL: <https://trac.macports.org/ticket/59094#comment:7>
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