[CMake] Remove LLVM_ENABLE_IR_PGO Option (#155958)

It has been deprecated for eight years now
(a702fa1), and all users that I know of
are using LLVM_BUILD_INSTRUMENTED.

Author: boomanaiden154

llvm/cmake/modules/HandleLLVMOptions.cmake

@@ -1172,16 +1172,13 @@ if(LLVM_ENABLE_EH AND NOT LLVM_ENABLE_RTTI)
   message(FATAL_ERROR "Exception handling requires RTTI. You must set LLVM_ENABLE_RTTI to ON")
 endif()
 
-option(LLVM_ENABLE_IR_PGO "Build LLVM and tools with IR PGO instrumentation (deprecated)" Off)
-mark_as_advanced(LLVM_ENABLE_IR_PGO)
-
 set(LLVM_BUILD_INSTRUMENTED OFF CACHE STRING "Build LLVM and tools with PGO instrumentation. May be specified as IR or Frontend")
 set(LLVM_VP_COUNTERS_PER_SITE "1.5" CACHE STRING "Value profile counters to use per site for IR PGO with Clang")
 mark_as_advanced(LLVM_BUILD_INSTRUMENTED LLVM_VP_COUNTERS_PER_SITE)
 string(TOUPPER "${LLVM_BUILD_INSTRUMENTED}" uppercase_LLVM_BUILD_INSTRUMENTED)
 
 if (LLVM_BUILD_INSTRUMENTED)
-  if (LLVM_ENABLE_IR_PGO OR uppercase_LLVM_BUILD_INSTRUMENTED STREQUAL "IR")
+  if (uppercase_LLVM_BUILD_INSTRUMENTED STREQUAL "IR")
     append("-fprofile-generate=\"${LLVM_PROFILE_DATA_DIR}\""
       CMAKE_CXX_FLAGS
       CMAKE_C_FLAGS)