-funit-at-a-time is the default however some current makefiles pass -fno-unit-at-a-time which is ignored by GCC, we should warn about this not error out.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@83976 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Driver/Tools.cpp

@@ -914,7 +914,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Arg *A = Args.getLastArg(options::OPT_funit_at_a_time,
                                options::OPT_fno_unit_at_a_time)) {
     if (A->getOption().matches(options::OPT_fno_unit_at_a_time))
-      D.Diag(clang::diag::err_drv_clang_unsupported) << A->getAsString(Args);
+      D.Diag(clang::diag::warn_drv_clang_unsupported) << A->getAsString(Args);
   }
 
   // Default to -fno-builtin-str{cat,cpy} on Darwin for ARM.