src: update make for new code coverage locations

The files for code coverage are moving to the build
repository.  Update the references to reflect this.

PR-URL: https://github.com/nodejs/node/pull/17987


Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>