build: fix test failures not failing Travis builds

The exit code of the make command used to execute tests was being lost
after being piped through to grep.

PR-URL: https://github.com/nodejs/node/pull/27176


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>