[libcxx] [llvm] Add C++23 stacktrace (P0881R7) (PR #136528)

[A. Jiang via llvm-commits]

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@@ -0,0 +1,191 @@
+// -*- C++ -*-
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frederick-vs-ja wrote:

Thanks!

But while `stacktrace` is now experimental, we should place the headers to the usual place (i.e. under `libcxx/include/` directly). `<experimental/...>` is for features from some technical specializations (TS) that are not standardized yet.

https://github.com/llvm/llvm-project/pull/136528