Clang change: Do not inline hot callsites for samplepgo in thinlto compile phase.

Summary:
Because SamplePGO passes will be invoked twice in ThinLTO build: once at compile phase, the other at backend. We want to make sure the IR at the 2nd phase matches the hot part in pro
file, thus we do not want to inline hot callsites in the first phase.

Reviewers: tejohnson, eraman

Reviewed By: tejohnson

Subscribers: mehdi_amini, cfe-commits, Prazek

Differential Revision: https://reviews.llvm.org/D31202

llvm-svn: 298429