[Bug c/68833] [6 Regression] -Werror=format issues an error now

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68833

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 37000
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37000&action=edit
gcc6-pr68833.patch

Untested fix.