Object libraries are weird, and producing a library by using the
target objects from them doesn't automatically import the interface
properties of the linked targets. These object libraries only have
single uses, so just directly create the final library from the
sources.
Leaves libelf as an object library, since there seems to be some cmake
oddity when trying to link an unexported target to an exported one.
Change-Id: Ic379612c89340c40085c9862cfe111fa4bbff425
Matt Arsenault
cba7a4d20e