fchdir

fn fchdir(sync: *CancelRegion.Sync, dir: fd_t) process.SetCurrentDirError!void {
    if (dir == linux.AT.FDCWD) return;
    while (true) {
        try sync.cancel_region.await(.nothing);
        switch (linux.errno(linux.fchdir(dir))) {
            .SUCCESS => return,
            .INTR => {},
            .ACCES => return error.AccessDenied,
            .NOTDIR => return error.NotDir,
            .IO => return error.FileSystem,
            .BADF => |err| return errnoBug(err),
            else => |err| return unexpectedErrno(err),
        }
    }
}