Commit ae3251851 changed the fprintf() format argument into a variable
which triggers a gcc 6.3 warning/error:
src/fstab-generator/fstab-generator.c:243:17: error: format not a string literal,
argument types not checked [-Werror=format-nonliteral]
fprintf(f, format, res);
This is a false positive, as the function is only being called with
constant (not user-definable) arguments which are valid format strings.