[clang] [clang][NFC] Update isAuxBuiltinID comment (PR #128038)

[Erich Keane via cfe-commits]

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@@ -408,7 +408,9 @@ class Context {
 
   unsigned getRequiredVectorWidth(unsigned ID) const;
 
-  /// Return true if builtin ID belongs to AuxTarget.
+  /// Return true if builtin ID belongs to only the AuxTarget.
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erichkeane wrote:

Perhaps, "Return true if the builtin ID belongs exclusively to the AuxTarget, and false if it belongs to both primary and aux target, or neither."

WDYT?

https://github.com/llvm/llvm-project/pull/128038