Console warning because `build/.../underscore.min.js` references `sourceMapURL` that doesn't exist

[iandunn]

r43138 introduced a regression where build/wp-include/js/underscore.min.js has an invalid sourceMapURL value:

//# sourceMappingURL=underscore-min.map

This results in a warning in the browser console:

Source map error: request failed with status 404
Resource URL: http://wp-develop.test/wp-includes/js/underscore.min.js?ver=1.8.3

[iandunn]

Related r25072, r37723

[arcturusink]

I was able to replicate the warning.

However, I can't find the underscore.min.js file anywhere inside the src directory, so confused as to how to proceed with the issue.

[laghee]

I was able to reproduce the console warning, and I'm attaching a patch that should fix this.

I needed to add both underscore-min.map and underscore.js to the section of the Gruntfile that copies over npm-package files. Adding only the map file didn't eliminate the error (because the map lists underscore.js with the "sources" key).

If there's a better approach or change needed, I'm happy to comply. Thx!

[netweb]

Patch 44560.diff​ needs a refresh following [44529]

[pento]

In 44632:

Build Tools: Uglify underscore.min.js while building.

This avoids a sourceMappingURL being in the minified file, as we don't ship source maps.

Props pento, laghee.
Fixes #44560.