[MacPorts] #44381: graphviz, graphviz-devel: Add port:flex build dependency

[MacPorts]

#44381: graphviz, graphviz-devel: Add port:flex build dependency
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  Reporter:  michaelld                |      Owner:  ryandesign
      Type:  defect                   |     Status:  new
  Priority:  Normal                   |  Milestone:
 Component:  ports                    |    Version:  2.3.1
Resolution:                           |   Keywords:
      Port:  graphviz graphviz-devel  |
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Comment (by ryandesign):

 Sorry, I was wrong. #58457 was not a duplicate.

 I have not seen a failure building the graphviz ports with macOS flex. And
 indeed some users have reported problems building graphviz and other
 MacPorts software when using MacPorts flex; #58457 is one such instance.
 Other tickets point at possible conflicting files installed by Homebrew
 being the cause of the problem, but I don't think we've ever gotten a
 definitive analysis and solution.

 So I don't feel that adding a flex dependency would help this port.

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Ticket URL: <https://trac.macports.org/ticket/44381#comment:4>
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