[MacPorts] #61691: legacy-support: add clock_gettime_nsec_np and CLOCK_UPTIME_RAW

[MacPorts]

#61691: legacy-support: add clock_gettime_nsec_np and CLOCK_UPTIME_RAW
-----------------------------------------+--------------------
  Reporter:  ryandesign                  |      Owner:  (none)
      Type:  enhancement                 |     Status:  new
  Priority:  Normal                      |  Milestone:
 Component:  ports                       |    Version:
Resolution:                              |   Keywords:
      Port:  legacy-support, php-xdebug  |
-----------------------------------------+--------------------

Comment (by kencu):

 As of OS X 10.12, the clock handling in darwin became more finely
 resolved. There is also an issue now building libcxx-11 (which is part of
 building clang-11) on < 10.12 due to this clock issue.

 The libcxx source code had a fallback that was used until recently, when
 it was deleted here [https://github.com/llvm/llvm-
 project/commit/babd3aefc9193b44ad0620a2cfd63ebb6ad7e952#diff-
 f3cc143394a9c0c9adc91467991535414b6444b46a8a3253f95c6c0e0eca4c2a here].

 To get newer clangs building on older systems we'll have to reinstate that
 fallback, and perhaps it might in the end be done in legacysupport... have
 to look at it closely to see how it fits in with what we already have
 there, and whether it might serve as the basis for this missing function.

-- 
Ticket URL: <https://trac.macports.org/ticket/61691#comment:1>
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