Include bpf program in APEXes

bpf program is put to an APEX via 'bpfs' property. It is
placed under etc/bpf directory in it.

Fix: 167530625
Test: m
Change-Id: Ia36b486f0cffb619ecc4f7a318cde881abc5baf4

bpf/bpf.go

@@ -26,7 +26,7 @@ import (
 )
 
 func init() {
-	android.RegisterModuleType("bpf", bpfFactory)
+	android.RegisterModuleType("bpf", BpfFactory)
 	pctx.Import("android/soong/cc/config")
 }
 
@@ -43,6 +43,13 @@ var (
 		"ccCmd", "cFlags")
 )
 
+// BpfModule interface is used by the apex package to gather information from a bpf module.
+type BpfModule interface {
+	android.Module
+
+	OutputFiles(tag string) (android.Paths, error)
+}
+
 type BpfProperties struct {
 	Srcs         []string `android:"path"`
 	Cflags       []string
@@ -141,7 +148,7 @@ func (bpf *bpf) OutputFiles(tag string) (android.Paths, error) {
 
 var _ android.OutputFileProducer = (*bpf)(nil)
 
-func bpfFactory() android.Module {
+func BpfFactory() android.Module {
 	module := &bpf{}
 
 	module.AddProperties(&module.properties)