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Stepan Ulyanin
db01d87942
Adds three new system call wrappers for the `symlinkat`, `renameatx_np`, and `unlinkat` system calls. ### Motivation: Related to https://github.com/apple/swift-nio/issues/3403 and https://github.com/apple/swift-nio/pull/3470. This PR adds syscall wrappers needed to atomically overwrite existing files or symlinks at the destination during copy operations. On Linux, atomic overwrites require a "copy to temp file, then rename" strategy. We use the `*at` family of syscalls (which operate relative to directory file descriptors) to avoid TOCTOU race conditions. ### Modifications: 1. Adds three system call wrappers for the `symlinkat`, `renameatx_np`, and `unlinkat` system calls. 2. Adds related tests 3. Updates the `FileSystemError` for `symlink` and `unlink` to take in the system call name to allow for the `*at` names to be passed.