[MacPorts] #57694: clang-6.0: build fails in compiler_rt on < SnowLeopard due to fatal error: 'dispatch/dispatch.h' file not found

[MacPorts]

#57694: clang-6.0: build fails in compiler_rt on < SnowLeopard due to fatal error:
'dispatch/dispatch.h' file not found
------------------------+---------------------------
  Reporter:  kencu      |      Owner:  jeremyhu
      Type:  defect     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:  tiger leopard
      Port:  clang-6.0  |
------------------------+---------------------------

Comment (by kencu):

 I'll put up the patched version of `compiler-
 rt/lib/builtins/os_version_check.c` with a small test program attached to
 it to drive it.

 It works for me on 10.4 and up, building it with:
 {{{
 clang -Wall -framework CoreFoundatation -o test_osversion
 ken_os_version_check_clang-6.c
 }}}
 or
 {{{
 gcc -Wall -framework CoreFoundatation -o test_osversion
 ken_os_version_check_clang-6.c
 }}}
 Interestingly, if you don't link in CoreFoundation the code does not
 error, but does not actually run the test or do anything either. Should
 probably return "-1" or something in that case, but have to ask the
 compiler_rt guys about that I guess :>

-- 
Ticket URL: <https://trac.macports.org/ticket/57694#comment:3>
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