internal/poll,net: support poll.Sendfile for darwin

darwin already supports syscall.Sendfile.

Change-Id: Id3db06591ffad0550b4173bacddeb0acfe355f9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/355109
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Alexander Rakoczy <alex@golang.org>
diff --git a/src/internal/poll/sendfile_bsd.go b/src/internal/poll/sendfile_bsd.go
index 3ba30a2..5531e53 100644
--- a/src/internal/poll/sendfile_bsd.go
+++ b/src/internal/poll/sendfile_bsd.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build dragonfly || freebsd
-// +build dragonfly freebsd
+//go:build darwin || dragonfly || freebsd
+// +build darwin dragonfly freebsd
 
 package poll
 
diff --git a/src/net/sendfile_stub.go b/src/net/sendfile_stub.go
index 5753bc0..c079064 100644
--- a/src/net/sendfile_stub.go
+++ b/src/net/sendfile_stub.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || (js && wasm) || netbsd || openbsd
-// +build aix darwin js,wasm netbsd openbsd
+//go:build aix || (js && wasm) || netbsd || openbsd
+// +build aix js,wasm netbsd openbsd
 
 package net
 
diff --git a/src/net/sendfile_unix_alt.go b/src/net/sendfile_unix_alt.go
index 54667d6..cd63dcc3 100644
--- a/src/net/sendfile_unix_alt.go
+++ b/src/net/sendfile_unix_alt.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build dragonfly || freebsd || solaris
-// +build dragonfly freebsd solaris
+//go:build darwin || dragonfly || freebsd || solaris
+// +build darwin dragonfly freebsd solaris
 
 package net