[llvm] [TableGen] Print a warning when a Processor contains duplicate Features / TuneFeatures (PR #137864)

[Rahul Joshi via llvm-commits]

================
@@ -333,6 +333,16 @@ unsigned SubtargetEmitter::cpuNames(raw_ostream &OS) {
   return Names.size();
 }
 
+static void checkDuplicateCPUFeatures(StringRef CPUName, StringRef FeatureKind,
+                                      ConstRecVec Features) {
----------------
jurahul wrote:

nit: use `ArrayRef<const Record *>` instead of `ConstRecVec`.?

https://github.com/llvm/llvm-project/pull/137864