Cast `getpid()` to `long long` before printing
Cast `getpid()` to `long long` before printing

Follow-up to commit 41441a65f.
That commit fixed the issue in runtime/ .
The present commit fixes the issue in ocamltest/ .

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml