[llvm] [Offload] Ensure all `llvm::Error`s are handled (PR #137339)

[Ross Brunton via llvm-commits]

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@@ -88,6 +89,17 @@ struct ol_impl_result_t {
     Result = errors().emplace(std::move(Err)).first->get();
   }
 
+  ol_impl_result_t(llvm::Error &&Error, llvm::StringRef Details) {
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RossBrunton wrote:

I'm not sure if this is better as a constructor or an explicit static `fromError` method.

https://github.com/llvm/llvm-project/pull/137339