runtime: remove unused pipe and setNonblock on linux/loong64
CL 389354 removed the fallback to pipe on all platforms with pipe2. This
is the case for linux. Thus, pipe and setNonblock are no longer needed
on linux/loong64 too.
Change-Id: I089adf918d0fd8de5d4d61a893707a2660f89183
Reviewed-on: https://go-review.googlesource.com/c/go/+/410736 Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>