report: fix stdout/stderr output formatting

This commit prevents the report and "report complete" message
from being printed on the same line.

PR-URL: https://github.com/nodejs/node/pull/26522


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>