Avoid LLVM-deprecated Optional::hasValue

LLVM 15 added `Optional::has_value`, and LLVM `main` (16) has deprecated
`hasValue`. However, its `explicit operator bool` does the same thing,
and was added long ago, so we can use that across our full LLVM range of
compatibility.

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -1044,7 +1044,7 @@ extern "C" void LLVMRustSetModulePIELevel(LLVMModuleRef M) {
 extern "C" void LLVMRustSetModuleCodeModel(LLVMModuleRef M,
                                            LLVMRustCodeModel Model) {
   auto CM = fromRust(Model);
-  if (!CM.hasValue())
+  if (!CM)
     return;
   unwrap(M)->setCodeModel(*CM);
 }