net: document that on macOS c-archive requires -lresolv

net: document that on macOS c-archive requires -lresolv

For #58159

Change-Id: Iff8e017c568be111c494992cb6fe62d469e0f981
Reviewed-on: https://go-review.googlesource.com/c/go/+/470917
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>