[ORC] Update ObjectTransformLayer signature

Summary:
Update ObjectTransformLayer::addObjectSet to take the object set by
value rather than reference and pass it to the base layer with move
semantics rather than copy, to match r258185's changes to
ObjectLinkingLayer.

Update the unit test to verify that ObjectTransformLayer's signature stays
in sync with ObjectLinkingLayer's.


Reviewers: lhames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D16414

llvm-svn: 258630