> Your patch includes an unintentional change, -Werror-implicit-function-declaration to -Werror=implicit-function-declaration.

This is intentional. -Werror=implicit-function-declaration and
-Werror-implicit-function-declaration are same meaning and there is no
reason only -Wimplicit-function-declaration keeps exceptional.
Apple made a lot of incompatibility changes in past. We can't believe
they never make the same mistake again.