[MacPorts] #59429: ocaml: Update to 4.12.0 and fix livecheck

[MacPorts]

#59429: ocaml: Update to 4.12.0 and fix livecheck
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  Reporter:  ryandesign  |      Owner:  pmetzger
      Type:  update      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:
      Port:  ocaml       |
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Comment (by pmetzger):

 BTW, at this point, an updated camlp4 is in, but camlp5 is broken, and it
 isn't clear if or when Chet Murthy is going to update the upstream. I've
 got a request in to him. Generally, anything still using camlp4 is
 obsolete (though we can still build it) and anything using camlp5 is
 fragile and dependent on a single maintainer.

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Ticket URL: <https://trac.macports.org/ticket/59429#comment:12>
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