[clang] [libcxx] [C++17] Support __GCC_[CON|DE]STRUCTIVE_SIZE (PR #89446)

[James Y Knight via cfe-commits]

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@@ -1792,6 +1792,11 @@ class TargetInfo : public TransferrableTargetInfo,
   /// Whether to support HIP image/texture API's.
   virtual bool hasHIPImageSupport() const { return true; }
 
+  /// The minimum offset between two objects to avoid false sharing.
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jyknight wrote:

Might add a comment here that this is not considered part of the ABI, and is okay to change, for clarity of future target maintainers.

https://github.com/llvm/llvm-project/pull/89446