[MacPorts] #57539: legacysupport-1.0: Let ports specify what symbols they need

[MacPorts]

#57539: legacysupport-1.0: Let ports specify what symbols they need
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  Reporter:  ryandesign     |      Owner:  (none)
      Type:  defect         |     Status:  new
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:
Resolution:                 |   Keywords:
      Port:  legacysupport  |
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Comment (by ryandesign):

 Replying to [comment:4 cjones051073]:
 > The linker should already be dealing with this. It should only actually
 link the library if the target requires one of the symbols it provides.
 Otherwise the linkage should be dropped and not appear in the end
 binaries.

 Ah, I didn't consider that. Still, at the very least, an unneeded
 dependency is added. You already have
 `legacysupport.newest_darwin_requires_legacy` for specifying that the
 dependency etc. should not be added. I'm suggesting a more user-friendly
 way of specifying that.

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Ticket URL: <https://trac.macports.org/ticket/57539#comment:6>
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