[clang] [clang] Factor out OpenACC part of `Sema` (PR #84184)

[via cfe-commits]

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@@ -1162,6 +1162,11 @@ class Sema final {
   /// CurContext - This is the current declaration context of parsing.
   DeclContext *CurContext;
 
+  SemaOpenACC &OpenACC() {
+    assert(OpenACCPtr);
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cor3ntin wrote:

Sure. But that's not yet the case. I think we should add the asserts if and then, not everywhere.
Otherwise they might have a noticeable impact on assertion build

https://github.com/llvm/llvm-project/pull/84184