[clang] [Support] Deprecate system_endianness (PR #68279)

[Sergei Barannikov via cfe-commits]

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@@ -248,7 +248,7 @@ class HashBuilder : public HashBuilderBase<HasherT> {
   ///   template <typename HasherT, support::endianness Endianness>
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s-barannikov wrote:

This should've been updated too, I guess. Same below.


https://github.com/llvm/llvm-project/pull/68279