Function _assert_failed

Fleece/Support/betterassert.cc:54–59

#ifdef __cpp_exceptions
    __cold
    void _assert_failed(const char *cond, const char *fn, const char *file, int line) {
        throw assertion_failure(
                    log("FAILED ASSERTION `%s` in %s (at %s line %d)",
                        cond, fn, file, line));
    }

    __cold
    void _precondition_failed(const char *cond, const char *fn, const char *file, int line) {