Update the SamplePGO test to verify that unroll/icp is not invoked in thinlto compile phase.

Summary: This is the test added for https://reviews.llvm.org/D31217

Reviewers: tejohnson, mehdi_amini

Reviewed By: tejohnson

Subscribers: cfe-commits, Prazek

Differential Revision: https://reviews.llvm.org/D31219

llvm-svn: 298647