Fix cross compile for make cross

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

system/calls_linux.go

@@ -136,3 +136,10 @@ func Mkfifo(name string, mode uint32) error {
 func Umask(mask int) int {
 	return syscall.Umask(mask)
 }
+
+func SetCloneFlags(cmd *exec.Cmd, flag uintptr) {
+	if cmd.SysProcAttr == nil {
+		cmd.SysProcAttr = &syscall.SysProcAttr{}
+	}
+	cmd.SysProcAttr.Cloneflags = flag
+}

system/errors.go

@@ -0,0 +1,9 @@
+package system
+
+import (
+	"errors"
+)
+
+var (
+	ErrNotSupportedPlatform = errors.New("platform and architecture is not supported")
+)

system/setns_linux.go

@@ -1,16 +1,11 @@
 package system
 
 import (
-	"errors"
 	"fmt"
 	"runtime"
 	"syscall"
 )
 
-var (
-	ErrNotSupportedPlatform = errors.New("platform and architecture is not supported")
-)
-
 // Via http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7b21fddd087678a70ad64afc0f632e0f1071b092
 //
 // We need different setns values for the different platforms and arch

system/unsupported.go

@@ -0,0 +1,15 @@
+// +build !linux
+
+package system
+
+import (
+	"os/exec"
+)
+
+func SetCloneFlags(cmd *exec.Cmd, flag uintptr) {
+
+}
+
+func UsetCloseOnExec(fd uintptr) error {
+	return ErrNotSupportedPlatform
+}