[llvm] [Offload] Use llvm::Error throughout liboffload internals (PR #140879)

[Joseph Huber via llvm-commits]

================
@@ -69,48 +69,29 @@ struct ErrPtrHash {
 using ErrSetT = std::unordered_set<ErrPtrT, ErrPtrHash, ErrPtrEqual>;
 ErrSetT &errors();
 
-struct ol_impl_result_t {
-  ol_impl_result_t(std::nullptr_t) : Result(OL_SUCCESS) {}
-  ol_impl_result_t(ol_errc_t Code) {
-    if (Code == OL_ERRC_SUCCESS) {
-      Result = nullptr;
-    } else {
-      auto Err = std::unique_ptr<ol_error_struct_t>(
-          new ol_error_struct_t{Code, nullptr});
-      Result = errors().emplace(std::move(Err)).first->get();
-    }
+namespace {
+ol_errc_t GetErrorCode(std::error_code Code) {
+  if (Code.category() ==
+      error::make_error_code(error::ErrorCode::SUCCESS).category()) {
+    return static_cast<ol_errc_t>(Code.value());
   }
----------------
jhuber6 wrote:

```suggestion
      error::make_error_code(error::ErrorCode::SUCCESS).category())
    return static_cast<ol_errc_t>(Code.value());
```

https://github.com/llvm/llvm-project/pull/140879