[libc-commits] [libc] [libc][docs] Add a sunset policy to porting docs (PR #168936)

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github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

The build succeeded and no tests ran. This is expected in some build configurations.

https://github.com/llvm/llvm-project/pull/168936