[MacPorts] #61584: Use deployment target 10.16 on Big Sur

[MacPorts]

#61584: Use deployment target 10.16 on Big Sur
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  Reporter:  ryandesign   |      Owner:  (none)
      Type:  enhancement  |     Status:  new
  Priority:  High         |  Milestone:  MacPorts 2.7.0
 Component:  base         |    Version:  2.6.4
Resolution:               |   Keywords:  bigsur
      Port:               |
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Comment (by mcmara):

 Keep in mind that adding '''macosx_deployment_target 10.16''' to
 macports.conf will fix indeed some ports build, but it will break some
 others (for example '''gdk-pixbuf2'''). After upgrading to macOS 11, I
 have to continuously comment and uncomment the above depending by the port
 being built.

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Ticket URL: <https://trac.macports.org/ticket/61584#comment:6>
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