[MacPorts] #54365: eigen3 fails to configure on Sierra

[MacPorts]

#54365: eigen3 fails to configure on Sierra
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  Reporter:  TimArnold  |      Owner:  eborisch
      Type:  defect     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:
      Port:  eigen3     |
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Comment (by nablamalnabla):

 Other ports are up-to-date, and Xcode command line tools as well..
 On starting Xcode once, I got a prompt 'additional components required' to
 which I responded 'install', however, this has not fixed the configure
 failure.

 I am not sure why I have +clang39 active; but it might have been required
 from the dependent port (py27-graph-tool) which also has the option
 +clang39. So I am also not sure if I can just install eigen3 without it.
 As a last resort, I could try to re-install py-graph-tool from scratch
 without that option; it seems to be the only port that requires eigen3 on
 my system.

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Ticket URL: <https://trac.macports.org/ticket/54365#comment:17>
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