Build Tools: Don't include `.map` files in the build.

These files are fairly large, and while they're useful in development, they're not needed in the final build.

Props pento, mcsf.
Merges [43931] and [43932] to trunk.
See #45201.
Built from https://develop.svn.wordpress.org/trunk@44282


git-svn-id: https://core.svn.wordpress.org/trunk@44112 1a063a9b-81f0-0310-95a4-ce76da25c4cd