Use distutils to build the Sage library inplace to save on space / make it clearer which files are actually being used in runtime.

See the discussion at http://groups.google.com/group/sage-devel/browse_thread/thread/d5aef15acc4d178b

Depends on #13363

CC: @williamstein @kini @fchapoton @jhpalmieri

Component: build

Reviewer: John Palmieri

Issue created by migration from https://trac.sagemath.org/ticket/12659