feat: resolve compile errors in x-pack/audibeat without cgo

only enable af_packet module if cgo is enabled
drop cgo dependency from system module

x-pack/auditbeat/module/system/socket/dns/afpacket/afpacket.go

@@ -2,8 +2,7 @@
 // or more contributor license agreements. Licensed under the Elastic License;
 // you may not use this file except in compliance with the Elastic License.
 
-//go:build linux
-// +build linux
+//go:build linux && cgo
 
 package afpacket
 

x-pack/auditbeat/module/system/socket/guess/creds.go

@@ -19,16 +19,12 @@ import (
 	"github.com/elastic/elastic-agent-libs/mapstr"
 )
 
-/*
-struct mq_attr {
-	long mq_flags;
-	long mq_maxmsg;
-	long mq_msgsize;
-	long mq_curmsgs;
-	long __reserved[4];
-};
-*/
-import "C"
+type MqAttr struct {
+	_       int
+	Maxmsg  int
+	Msgsize int
+	_       int
+}
 
 /*
 	creds guess discovers the offsets of (E)UID/(E)GID fields within a
@@ -157,9 +153,9 @@ func (g *guessStructCreds) Trigger() error {
 	if err != nil {
 		return err
 	}
-	attr := C.struct_mq_attr{
-		mq_maxmsg:  1,
-		mq_msgsize: 8,
+	attr := MqAttr{
+		Maxmsg:  1,
+		Msgsize: 8,
 	}
 	mqd, _, errno := syscall.Syscall6(unix.SYS_MQ_OPEN,
 		uintptr(unsafe.Pointer(name)),