Force C++ mode in aksetup to avoid Clang error on -std=c++14

#1

aksetup_helper.py

@@ -941,7 +941,13 @@ class PybindBuildExtCommand(NumpyBuildExtCommand):
         opts = self.c_opts.get(ct, [])
         if ct in ['unix', 'mingw32']:
             opts.append('-DVERSION_INFO="%s"' % self.distribution.get_version())
+
+            # Force language to C++ to avoid Clang barking at us about an invalid flag for C.
+            # https://gitlab.tiker.net/inducer/pymetis/issues/1
+            opts.extend(["-x", "c++"])
+
             opts.append(cpp_flag(self.compiler))
+
             if has_flag(self.compiler, '-fvisibility=hidden'):
                 opts.append('-fvisibility=hidden')
         elif ct == 'msvc':