[MacPorts] #69867: legacy-support headers should work with later SDK versions

[MacPorts]

#69867: legacy-support headers should work with later SDK versions
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  Reporter:  fhgwright       |      Owner:  fhgwright
      Type:  defect          |     Status:  assigned
  Priority:  Low             |  Milestone:
 Component:  ports           |    Version:  2.9.3
Resolution:                  |   Keywords:
      Port:  legacy-support  |
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Comment (by fhgwright):

 Another case where this would fail is building on 10.4 with a 10.5+ SDK.
 The headers provided by 10.4 `legacy-support` to correct the omissions in
 the 10.4 SDK would override the non-omitted versions in the 10.5+ SDK,
 with a variety of potential problems.  The decision to incorporate the
 "missing" headers needs to be made at the time the headers are ''used'',
 not the time they're ''installed''.

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Ticket URL: <https://trac.macports.org/ticket/69867#comment:6>
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