[MacPorts] #57117: upgrade last users of protobuf-cpp to protobuf3-cpp

[MacPorts]

#57117: upgrade last users of protobuf-cpp to protobuf3-cpp
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  Reporter:  pmetzger                            |      Owner:  (none)
      Type:  enhancement                         |     Status:  new
  Priority:  Normal                              |  Milestone:
 Component:  ports                               |    Version:
Resolution:                                      |   Keywords:
      Port:  caffe MyPaint opencv raceintospace  |
  shogun-devel sumo                              |
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Comment (by ryandesign):

 Replying to [comment:13 kencu]:
 > Replying to [comment:11 ryandesign]:
 > > I'm suggesting putting the flag in protobuf.pc (and protobuf-lite.pc
 if applicable).
 > what if the port using protobuf actually needs `-std=c++14` or some
 newer standard than that? Then that flag from protobuf would mess things
 up...

 Upon reflection, you're probably right. Which leaves us back with needing
 to fix each port that uses protobuf individually.

 > In addition, it seems that pkg-config is not currently set up to
 (easily) pass CXXFLAGS <https://stackoverflow.com/questions/46550299/why-
 doesnt-pkg-config-support-cxxflags>...

 Amazing. It's a wonder anything builds at all!

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Ticket URL: <https://trac.macports.org/ticket/57117#comment:14>
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