[clang] Fix the behavior of __COUNT__ macros when PCH is enabled (PR #105591)

[via cfe-commits]

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@@ -1243,12 +1247,19 @@ bool ASTUnit::Parse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
   }
 
   std::unique_ptr<TopLevelDeclTrackerAction> Act(
-      new TopLevelDeclTrackerAction(*this));
+      new TopLevelDeclTrackerAction(*this, true));
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cor3ntin wrote:

Moreover, can you explain the "reuse  preprocessor" logic, which seems orthogonal to the goal of preserving `__COUNT__`? (ie, i would expect count to be preserved, not the whole preprocessor).
Unless I am missing something, I think this would simplify the patch a bit.

https://github.com/llvm/llvm-project/pull/105591