Create SampleProfileLoader pass in llvm instead of clang

Summary:
We used to create SampleProfileLoader pass in clang. This makes LTO/ThinLTO unable to add this pass in the linker plugin. This patch moves the SampleProfileLoader pass creation from
clang to llvm pass manager builder.

Reviewers: tejohnson, davidxl, dnovillo

Subscribers: mehdi_amini, cfe-commits

Differential Revision: https://reviews.llvm.org/D27744

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289715 91177308-0d34-0410-b5e6-96231b3b80d8