syscall: avoid dup2 in forkAndExecInChild1 on Android

Android O and newer blocks the dup2 syscall.

Change-Id: Ibca01fc72ef114deeef6c0450a8b81a556ed0530
Reviewed-on: https://go-review.googlesource.com/c/go/+/235537
Run-TryBot: Elias Naur <mail@eliasnaur.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/syscall/syscall_dup2_linux.go

@@ -0,0 +1,10 @@
+// Copyright 2020 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.
+
+// +build !android
+// +build 386 amd64 arm mips mipsle mips64 mips64le ppc64 ppc64le s390x
+
+package syscall
+
+const _SYS_dup = SYS_DUP2

src/syscall/syscall_dup3_linux.go

@@ -0,0 +1,9 @@
+// Copyright 2020 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.
+
+// +build android arm64 riscv64
+
+package syscall
+
+const _SYS_dup = SYS_DUP3

src/syscall/syscall_linux_386.go

@@ -9,10 +9,7 @@ package syscall
 
 import "unsafe"
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS32
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS32
-)
 
 func setTimespec(sec, nsec int64) Timespec {
 	return Timespec{Sec: int32(sec), Nsec: int32(nsec)}

src/syscall/syscall_linux_amd64.go

@@ -4,10 +4,7 @@
 
 package syscall
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 //sys	Dup2(oldfd int, newfd int) (err error)
 //sysnb	EpollCreate(size int) (fd int, err error)

src/syscall/syscall_linux_arm.go

@@ -6,10 +6,7 @@ package syscall
 
 import "unsafe"
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS32
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS32
-)
 
 func setTimespec(sec, nsec int64) Timespec {
 	return Timespec{Sec: int32(sec), Nsec: int32(nsec)}

src/syscall/syscall_linux_arm64.go

@@ -6,10 +6,7 @@ package syscall
 
 import "unsafe"
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP3
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 func EpollCreate(size int) (fd int, err error) {
 	if size <= 0 {

src/syscall/syscall_linux_mips64x.go

@@ -7,10 +7,7 @@
 
 package syscall
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 //sys	Dup2(oldfd int, newfd int) (err error)
 //sysnb	EpollCreate(size int) (fd int, err error)

src/syscall/syscall_linux_mipsx.go

@@ -9,10 +9,7 @@ package syscall
 
 import "unsafe"
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 func Syscall9(trap, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err Errno)
 

src/syscall/syscall_linux_ppc64x.go

@@ -7,10 +7,7 @@
 
 package syscall
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 //sys	Dup2(oldfd int, newfd int) (err error)
 //sysnb	EpollCreate(size int) (fd int, err error)

src/syscall/syscall_linux_riscv64.go

@@ -6,10 +6,7 @@ package syscall
 
 import "unsafe"
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP3
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 func EpollCreate(size int) (fd int, err error) {
 	if size <= 0 {

src/syscall/syscall_linux_s390x.go

@@ -6,10 +6,7 @@ package syscall
 
 import "unsafe"
 
-const (
+const _SYS_setgroups = SYS_SETGROUPS
-	_SYS_dup       = SYS_DUP2
-	_SYS_setgroups = SYS_SETGROUPS
-)
 
 //sys	Dup2(oldfd int, newfd int) (err error)
 //sysnb	EpollCreate(size int) (fd int, err error)