[cmake] Add an option to build llvm with IR PGO

This adds an LLVM_ENABLE_IR_PGO option to enable building llvm and its
tools with IR PGO instrumentation.

Usage: -DLLVM_BUILD_INSTRUMENTED=On -DLLVM_ENABLE_IR_PGO=On (both
options must be enabled)

Differential Revision: https://reviews.llvm.org/D38066

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313770 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed