orc: Apply warning-as-errors for implicit function declarations
Hi!
This is a MR from !111 (merged) that enables erroring out when a function isn't defined. (The alternative is to enable C99 wholesale, which under MSVC means that we must jump to C11.)
This is useful for having compiles fail when porting a ruleset, instead of wait until the linker spams the console, or the runtime loader crashes the tests (eg. macOS).