syscall, os: use pipe2 syscall on FreeBSD instead of pipe

The pipe2 syscall exists in all officially supported FreeBSD
versions: 10, 11 and future 12.
The pipe syscall no longer exists in 11 and 12. To build and
run Go on these versions, kernel needs COMPAT_FREEBSD10 option.

Based on Gleb Smirnoff's https://golang.org/cl/38422

Fixes #18854

Change-Id: I8e201ee1b15dca10427c3093b966025d160aaf61
Reviewed-on: https://go-review.googlesource.com/38426
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/syscall/exec_freebsd.go b/src/syscall/exec_freebsd.go
new file mode 100644
index 0000000000..1654b4ba2a
--- /dev/null
+++ b/src/syscall/exec_freebsd.go
@@ -0,0 +1,9 @@
+// Copyright 2017 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 syscall
+
+func forkExecPipe(p []int) error {
+	return Pipe2(p, O_CLOEXEC)
+}