[MacPorts] #70207: c-ares @1.30.0_0: fatal error: 'os/availability.h' file not found

[MacPorts]

#70207: c-ares @1.30.0_0: fatal error: 'os/availability.h' file not found
-------------------------+-------------------------------------------------
  Reporter:              |      Owner:  tobypeterson
  sambthompson           |
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.9.3
Resolution:              |   Keywords:  mountainlion mavericks yosemite
      Port:  c-ares      |  elcapitan
-------------------------+-------------------------------------------------

Comment (by ryandesign):

 The reason c-ares checks for macOS 10.12 or later appears to be because
 that's when `clock_gettime` was introduced. It looks like it uses the
 check to skip some `clock_gettime` functionality on older systems.

 MacPorts has the legacy-support library which includes an implementation
 of `clock_gettime` for older systems which could be used if needed. The
 c-ares port doesn't use this yet.

 We can include a workaround like we did for xar, but we do not want to
 carry patches forever. The correct place to report software bugs is to the
 software's developers. If the developers fix it, we can backport their
 fix. If they refuse to fix it, then we can attempt our own patch.

-- 
Ticket URL: <https://trac.macports.org/ticket/70207#comment:4>
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