WIP: Try to properly filter static libraries

Adds a global split rule for static libraries, which is filtered out of the desktop stack in desktop-filter-static.bst. The static libraries we explicitly want to include are re-introduced into platform image by static-libraries.bst, which introduces a static-whitelist domain for split rules. Adding libraries to the whitelist is just a matter of adding them to this domain in this element. I think this should work correctly, but I may need to rework where the filtering happens to avoid leaking libraries through.

Closes #744 (closed) #740 (closed)