[IROutliner] Adding option to enable outlining from linkonceodr functions

There are functions that the linker is able to automatically
deduplicate, we do not outline from these functions by default. This
allows for outlining from those functions.

Tests:
llvm/test/Transforms/IROutliner/outlining-odr.ll

Reviewers: jroelofs, paquette

Differential Revision: https://reviews.llvm.org/D87309