[libc] [llvm] [libc] add remaining epoll functions, pipe (PR #84587)

[Nick Desaulniers via llvm-commits]

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@@ -11,7 +11,11 @@
 
 #include <llvm-libc-types/struct_epoll_data.h>
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nickdesaulniers wrote:

I think this needs to be adjusted to "struct_epoll_data.h", based on the build failures.
https://buildkite.com/llvm-project/github-pull-requests/builds/46591#018e348b-db56-4d69-a0a2-ca7d6daf9f76

https://github.com/llvm/llvm-project/pull/84587