Use OutputFilesProvider on filesystem module types

Test: CI
Bug: 339477385
Change-Id: I0902726cfef13c716d73c1abc5c9836bdcf3e10f
diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index d2572c2..c889dd6 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -221,6 +221,8 @@
 
 	f.installDir = android.PathForModuleInstall(ctx, "etc")
 	ctx.InstallFile(f.installDir, f.installFileName(), f.output)
+
+	ctx.SetOutputFiles([]android.Path{f.output}, "")
 }
 
 func validatePartitionType(ctx android.ModuleContext, p partition) {
@@ -561,16 +563,6 @@
 	}}
 }
 
-var _ android.OutputFileProducer = (*filesystem)(nil)
-
-// Implements android.OutputFileProducer
-func (f *filesystem) OutputFiles(tag string) (android.Paths, error) {
-	if tag == "" {
-		return []android.Path{f.output}, nil
-	}
-	return nil, fmt.Errorf("unsupported module reference tag %q", tag)
-}
-
 // Filesystem is the public interface for the filesystem struct. Currently, it's only for the apex
 // package to have access to the output file.
 type Filesystem interface {