[cmake] Allow LLVM_BUILD_INSTRUMENTED to be set to IR or Frontend

- This deprecates LLVM_ENABLE_IR_PGO but keeps it around for now.
- Errors out when LLVM_BUILD_INSTRUMENTED and LLVM_BUILD_INSTRUMENTED_COVERAGE
  are both set.

Motivated by bogner's post-commit review of r313770.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317725 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed