[llvm] [LangRef] Add hybrid_patchable attribute description (PR #219806)

[Eli Friedman via llvm-commits]

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@@ -2273,6 +2273,13 @@ define void @f() "no-sse" { ... }
     around the cases where the training input does not have good coverage
     on all the hot functions.
 
+`hybrid_patchable`
+:   This attribute indicates that an ARM64EC function may be patched at runtime.
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efriedma-quic wrote:

Probably this should start with something like "This attribute applies to code compiled for ARM64EC (target triple 'arm64ec-*') targets.", so the context is clear.

https://github.com/llvm/llvm-project/pull/219806