[MacPorts] #59660: py36-isce2 fails to rebuild with Xcode 11.2

[MacPorts]

#59660: py36-isce2 fails to rebuild with Xcode 11.2
-------------------------+--------------------
  Reporter:  EJFielding  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.6.2
Resolution:              |   Keywords:
      Port:  py36-isce2  |
-------------------------+--------------------

Comment (by EJFielding):

 I found that my gcc7 installation was not working because it was linked to
 the MacOSX10.14.sdk in the Xcode directory, which is no longer available
 with Xcode 11.x.

 I asked on the MacPorts mailing list and Chris Jones suggested:

 {{{
 You might need to manually force a CLT update, as its possible it is not
 being correctly updated. See

 https://trac.macports.org/wiki/ProblemHotlist#reinstall-clt
 }}}

 This did not completely solve the problem because the gcc7 pre-compiled
 binary was still linked to the MacOSX10.14.sdk in the Xcode directory. I
 then rebuilt the entire gcc7 from source (which took over an hour). I also
 ran `xcode-select -r` to reset the Xcode path.

 Now `xcrun --show-sdk-path` reports:
 {{{
 /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk
 }}}

 Now the gcc7 installation is working and I was able to get the GitHub
 source version of ISCE2 to compile (this was failing before as gcc was not
 able to compile anything that depends on the SDK). The rebuild of the
 py36-isce2 port still fails, however. I attach the new main.log file.

-- 
Ticket URL: <https://trac.macports.org/ticket/59660#comment:2>
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