[MacPorts] #54289: libcxx{,-abi} : upgrade + "runtime" variant

[MacPorts]

#54289: libcxx{,-abi} : upgrade + "runtime" variant
-------------------------------+----------------------
  Reporter:  RJVB              |      Owner:  jeremyhu
      Type:  update            |     Status:  assigned
  Priority:  Normal            |  Milestone:
 Component:  ports             |    Version:
Resolution:                    |   Keywords:  haspatch
      Port:  libcxxabi libcxx  |
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Comment (by kencu):

 Funny, I had thought _cxa_atexit() was actually important to have
 <https://stackoverflow.com/questions/42912038/what-is-the-difference-
 between-cxa-atexit-and-atexit>, <https://itanium-cxx-abi.github.io/cxx-
 abi/abi.html#dso-dtor-motivation>. But what do I know? See what Jeremy
 says, I guess.

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Ticket URL: <https://trac.macports.org/ticket/54289#comment:2>
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