[MacPorts] #62878: openmpi: fix builds for MacOS 10.8 and earlier; mark known_fail, for cases not easily fixable

[MacPorts]

#62878: openmpi: fix builds for MacOS 10.8 and earlier; mark known_fail, for cases
not easily fixable
----------------------+---------------------
  Reporter:  jmroot   |      Owner:  mascguy
      Type:  defect   |     Status:  closed
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:  fixed    |   Keywords:
      Port:  openmpi  |
----------------------+---------------------

Comment (by mascguy):

 Several of the disabled subports were still trying to build, due to
 unintended dependencies. (Both on the default subport, as well as `legacy-
 support` for earlier macOS releases.)

 That's been fixed as of this writing, and that should further reduce any
 wasted buildbot time.

-- 
Ticket URL: <https://trac.macports.org/ticket/62878#comment:23>
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