Fix fuzzer runner

[nielsdos]

We must take into account the calling convention of the tailcall vm.

[arnaud-lb]

Thank you!

[arnaud-lb]

Oh, however, opline->handler will not return immediately - it calls the next handler instead, so it will bypass the step limit.

I suggest to fetch the stepping-friendly handler func with zend_get_opcode_handler_func(), like in https://github.com/arnaud-lb/php-src/blob/73b98a385848f4800cf81392b09d648e8cd5a698/ext/opcache/jit/zend_jit_trace.c#L8921.

[nielsdos]

Okay done that now, but I wonder how expensive the hash+array lookup is :|