--- a/make/autoconf/flags-cflags.m4	Thu Apr 26 20:42:43 2018 +0200
+++ b/make/autoconf/flags-cflags.m4	Thu Apr 26 15:41:48 2018 +0200
@@ -128,16 +128,22 @@
   AC_ARG_ENABLE([warnings-as-errors], [AS_HELP_STRING([--disable-warnings-as-errors],
       [do not consider native warnings to be an error @<:@enabled@:>@])])
 
+  # Set default value.
+  if test "x$TOOLCHAIN_TYPE" = xxlc; then
+    WARNINGS_AS_ERRORS=false
+  else
+    WARNINGS_AS_ERRORS=true
+  fi
+
   AC_MSG_CHECKING([if native warnings are errors])
   if test "x$enable_warnings_as_errors" = "xyes"; then
     AC_MSG_RESULT([yes (explicitly set)])
     WARNINGS_AS_ERRORS=true
   elif test "x$enable_warnings_as_errors" = "xno"; then
-    AC_MSG_RESULT([no])
+    AC_MSG_RESULT([no (explicitly set)])
     WARNINGS_AS_ERRORS=false
   elif test "x$enable_warnings_as_errors" = "x"; then
-    AC_MSG_RESULT([yes (default)])
-    WARNINGS_AS_ERRORS=true
+    AC_MSG_RESULT([${WARNINGS_AS_ERRORS} (default)])
   else
     AC_MSG_ERROR([--enable-warnings-as-errors accepts no argument])
   fi