Fix: use pipe to spawn child process to re-enable file logging (#4293)

We pipe the child's stdout and stderr to the log file (and to the parent's streams) but since we used `inherit` for `stdio` this caused the child to use the parent's streams directly which made `child.stdout` and `child.stderr` non-existent and thus we had no file logging.

Using `pipe` creates stdin and stderr on the child.