[clang] [Clang][NFC] Fix out-of-bounds access (PR #77193)

[Yitzhak Mandelbaum via cfe-commits]

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@@ -1215,7 +1215,7 @@ class CFG {
   //===--------------------------------------------------------------------===//
 
   class BuildOptions {
-    std::bitset<Stmt::lastStmtConstant> alwaysAddMask;
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ymand wrote:

Maybe add a comment explaining the new size? I see why it might be obvious, but given that it was done incorrectly the first time, a comment seems warranted.

https://github.com/llvm/llvm-project/pull/77193