Reapply "[Clang][CMake] Use IRPGO instead of FE PGO for Cmake Caches" (llvm#160711)

This reverts commit 18f7e03.

Reapplies llvm#160133.

This was reverted originally because it was causing compilation crashes
in ControlHeightReduction. It was reverted again because fix in
CntrolHeightReduction was causing more problems. Everything should be in
working order now, so relanding.

Author: boomanaiden154

clang/cmake/caches/PGO.cmake

@@ -5,7 +5,7 @@ set(LLVM_ENABLE_PROJECTS "clang;lld" CACHE STRING "")
 set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
 
 set(LLVM_TARGETS_TO_BUILD Native CACHE STRING "")
-set(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED ON CACHE BOOL "")
+set(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED IR CACHE BOOL "")
 set(CLANG_BOOTSTRAP_TARGETS
   generate-profdata
   stage2