Build Tools: Copy un-minified JS to the src directory

[pento]

When running the SCRIPT_DEBUG set to true, we expect a bunch of un-minified JS files to exist, which currently aren't copied to their correct location in the src directory.

This is a followup to #44492.

[pento]

45869.diff​ fixes all of the missing files I've noticed:

• wp-includes/jquery/ui/*.js
• wp-includes/underscore.js
• wp-includes/tinymce/tinymce.js

@atimmer, @omarreiss, could you please review this and see if there's anything else missing?

[pento]

In 44529:

Build Tools: Copy unminified JS files to src.

This allows SCRIPT_DEBUG to be set to true when running from src.

Fixes #45869.

[westonruter]

I believe I've found another instance. When testing Twenty Fourteen I'm getting a 404 for /wp-includes/js/jquery/jquery.masonry.js?ver=3.1.2b

[desrosj]

Replying to westonruter:

I believe I've found another instance. When testing Twenty Fourteen I'm getting a 404 for /wp-includes/js/jquery/jquery.masonry.js?ver=3.1.2b

This is being addressed in #47353. As far as I can tell, the unminified version of jquery-masonry has never been included in Core. But this version only remains as a courtesy (see [27271]).