internal/poll: add SPLICE_F_NONBLOCK flag for splice to avoid inconsistency with O_NONBLOCK
For #59041
Details: https://github.com/golang/go/issues/59041#issuecomment-
1766610087
Change-Id: Id3fc1df6d86b7c4cc383d09f9465fa8f4cc2a559
Reviewed-on: https://go-review.googlesource.com/c/go/+/536015
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>