on qemu:
 forking-service.sh test always fail.


try use strace but can't:

```
+ /gnu/store/w7a3fxw00y4picvcrkvdxavpj5gqabbb-strace-6.2/bin/strace -f -t -s 80 -o /tmp/she.strace shepherd -I -s t-socket-25862 -c t-conf-25862 -l t-log-25862 --pid=t-pid-25862
+ sleep 0.3
/gnu/store/w7a3fxw00y4picvcrkvdxavpj5gqabbb-strace-6.2/bin/strace: test_ptrace_get_syscall_info: PTRACE_TRACEME: Function not implemented
/gnu/store/w7a3fxw00y4picvcrkvdxavpj5gqabbb-strace-6.2/bin/strace: ptrace(PTRACE_TRACEME, ...): Function not implemented
/gnu/store/w7a3fxw00y4picvcrkvdxavpj5gqabbb-strace-6.2/bin/strace: PTRACE_SETOPTIONS: Function not implemented
/gnu/store/w7a3fxw00y4picvcrkvdxavpj5gqabbb-strace-6.2/bin/strace: detach: waitpid(25922): No child processes
```

pid-file.sh fail in check phase, but success at rerun use 'make check TESTS=tests/pid-file.sh'


riscv machine temporarily unable to reproduce.