Revert "[CMake] Support a simple case for bootstrap builds to generate PGO data"

This reverts commit r256069, which was an unintentional tag along on
another commit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@256088 91177308-0d34-0410-b5e6-96231b3b80d8