m4: fix compilation on Sierra with GCC (#1844)

* m4: fix compilation on Sierra with GCC

* m4: check macOS version

var/spack/repos/builtin/packages/m4/package.py

@@ -23,6 +23,7 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 from spack import *
+import sys
 
 
 class M4(Package):
@@ -47,6 +48,11 @@ def install(self, spec, prefix):
         else:
             configure_args.append('--without-libsigsegv-prefix')
 
+        # http://lists.gnu.org/archive/html/bug-m4/2016-09/msg00002.html
+        if (sys.platform == "darwin") and (spec.satisfies('%gcc')) and \
+           (spec.architecture.platform_os.version == "10.12"):
+            configure_args.append('ac_cv_type_struct_sched_param=yes')
+
         configure("--prefix=%s" % prefix, *configure_args)
         make()
         make("install")