[llvm] [Offload] Implement `olShutDown` (PR #144055)

[Joseph Huber via llvm-commits]

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@@ -197,8 +195,10 @@ Error olInit_impl() {
   std::lock_guard<std::mutex> Lock{OffloadContextValMutex};
 
   std::optional<Error> InitResult;
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jhuber6 wrote:

A `std::optional<Error>` is weird here. The result of `Error::success()` is supposed to be the optional result.

https://github.com/llvm/llvm-project/pull/144055