[clang] [clang] Fix GNU spellings of lifetimebound/lifetime_capture_by (PR #192070)

[Zeyi Xu via cfe-commits]

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@@ -48,3 +48,15 @@ struct T {
   void explicit_this1(this T& self, const int &x [[clang::lifetime_capture_by(self)]]);
   void explicit_this2(this T& self, const int &x [[clang::lifetime_capture_by(this)]]); // expected-error {{argument references unavailable implicit 'this'}}
 };
+
+struct GNUCaptureBy {
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zeyi2 wrote:

https://godbolt.org/z/j5r5joad4

This previously would give an error

https://github.com/llvm/llvm-project/pull/192070