net, internal/poll, net/internal/socktest: use accept4 and SOCK_{CLOEXEC,NONBLOCK} on dragonfly

Fixes #14222

Change-Id: I026fc9499fdefc33b8bb58b5963e2290adacbf63
Reviewed-on: https://go-review.googlesource.com/40895Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/internal/poll/hook_cloexec.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd linux
+// +build dragonfly freebsd linux
 
 package poll
 

src/internal/poll/sock_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements sysSocket and accept for platforms that
 // provide a fast path for setting SetNonblock and CloseOnExec.
 
-// +build freebsd linux
+// +build dragonfly freebsd linux
 
 package poll
 

src/internal/poll/sys_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements sysSocket and accept for platforms that do not
 // provide a fast path for setting SetNonblock and CloseOnExec.
 
-// +build darwin dragonfly nacl netbsd openbsd solaris
+// +build darwin nacl netbsd openbsd solaris
 
 package poll
 

src/net/internal/socktest/sys_cloexec.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd linux
+// +build dragonfly freebsd linux
 
 package socktest
 

src/net/main_cloexec_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd linux
+// +build dragonfly freebsd linux
 
 package net
 

src/net/sock_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements sysSocket and accept for platforms that
 // provide a fast path for setting SetNonblock and CloseOnExec.
 
-// +build freebsd linux
+// +build dragonfly freebsd linux
 
 package net
 

src/net/sys_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements sysSocket and accept for platforms that do not
 // provide a fast path for setting SetNonblock and CloseOnExec.
 
-// +build darwin dragonfly nacl netbsd openbsd solaris
+// +build darwin nacl netbsd openbsd solaris
 
 package net