[LLVM] Accept noundef attribute in function definitions/calls

The `noundef` attribute indicates an argument or return value which
may never have an undef value representation.

This patch allows LLVM to parse the attribute.

Differential Revision: https://reviews.llvm.org/D83412

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -731,6 +731,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_SANITIZE_MEMTAG;
   case Attribute::Preallocated:
     return bitc::ATTR_KIND_PREALLOCATED;
+  case Attribute::NoUndef:
+    return bitc::ATTR_KIND_NOUNDEF;
   case Attribute::EndAttrKinds:
     llvm_unreachable("Can not encode end-attribute kinds marker.");
   case Attribute::None: