[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:  sambthompson                         |      Owner:
                                                 |  tobypeterson
     Type:  defect                               |     Status:  assigned
 Priority:  Normal                               |  Milestone:
Component:  ports                                |    Version:  2.9.3
 Keywords:  mountainlion mavericks yosemite      |       Port:  c-ares
  elcapitan                                      |
-------------------------------------------------+-------------------------
 c-ares @1.30.0_0 fails to build on OS X El Capitan (and earlier, back to
 Mountain Lion):

 https://build.macports.org/builders/ports-10.11_x86_64-builder/builds/268051/steps
 /install-port/logs/stdio

 {{{
 In file included from /opt/local/var/macports/build
 /_opt_bblocal_var_buildworker_ports_build_ports_net_c-
 ares/c-ares/work/c-ares-1.30.0/src/lib/ares_sysconfig_mac.c:54:
 /opt/local/var/macports/build
 /_opt_bblocal_var_buildworker_ports_build_ports_net_c-
 ares/c-ares/work/c-ares-1.30.0/src/lib/thirdparty/apple/dnsinfo.h:31:10:
 fatal error: 'os/availability.h' file not found
 }}}

 Prior version 1.28.1_0 not affected. OS versions prior (Lion/Snow Leopard)
 buildbot logs show different errors, not investigated.

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