--- clang/include/clang/Driver/Options.td.orig	2019-10-21 21:45:02.000000000 +0100
+++ clang/include/clang/Driver/Options.td	2019-10-22 00:00:39.833390000 +0100
@@ -1186,6 +1186,8 @@
   Flags<[CC1Option]>;
 def fno_use_line_directives : Flag<["-"], "fno-use-line-directives">, Group<f_Group>;
 
+def fformat_extensions: Flag<["-"], "fformat-extensions">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Enable FreeBSD kernel specific format string extensions">;
 def ffreestanding : Flag<["-"], "ffreestanding">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Assert that the compilation takes place in a freestanding environment">;
 def fgnuc_version_EQ : Joined<["-"], "fgnuc-version=">, Group<f_Group>,