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

[Ross Brunton via llvm-commits]

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@@ -162,8 +163,8 @@ def : Function {
   let name = "olShutDown";
   let desc = "Release the resources in use by Offload";
   let details = [
-    "All resources owned by the Offload library and plugins will be released",
-    "Subsequent API calls made after calling `olShutDown` are undefined behavior"
+    "This decrements an internal reference count. When this reaches 0, all resources will be released",
+    "Subsequent API calls to methods other than `olInit` made after resources are released are undefined behavior"
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RossBrunton wrote:

These are for functions other than `olInit`. That is, trying to use the offload API without initialising it first causes UB.

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