os: handle file creation with close-on-exec flag correctly on darwin, freebsd
Fixes #7187.
Update #7193
LGTM=bradfitz
R=golang-codereviews, dave, rsc, minux.ma, bradfitz
CC=golang-codereviews
https://golang.org/cl/64510043
diff --git a/src/pkg/os/sys_nacl.go b/src/pkg/os/sys_nacl.go
new file mode 100644
index 0000000..07907c8
--- /dev/null
+++ b/src/pkg/os/sys_nacl.go
@@ -0,0 +1,9 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+// supportsCloseOnExec reports whether the platform supports the
+// O_CLOEXEC flag.
+const supportsCloseOnExec = false
