Build system_other image in soong-only builds

This just builds an empty system_other image for now, the dexpreopt
files will be added in a followup change.

Bug: 390269431
Test: m --soong-only
Change-Id: Ic4a9bcb8b7ba1eb4444b3339d6c0b0cdfd485714
diff --git a/fsgen/super_img.go b/fsgen/super_img.go
index 5c23868..e353688 100644
--- a/fsgen/super_img.go
+++ b/fsgen/super_img.go
@@ -27,7 +27,12 @@
 	return partitionVars.ProductBuildSuperPartition
 }
 
-func createSuperImage(ctx android.LoadHookContext, partitions []string, partitionVars android.PartitionVariables) []string {
+func createSuperImage(
+	ctx android.LoadHookContext,
+	partitions []string,
+	partitionVars android.PartitionVariables,
+	systemOtherImageName string,
+) []string {
 	baseProps := &struct {
 		Name *string
 	}{
@@ -79,6 +84,10 @@
 	}
 	superImageProps.Partition_groups = partitionGroupsInfo
 
+	if systemOtherImageName != "" {
+		superImageProps.System_other_partition = proptools.StringPtr(systemOtherImageName)
+	}
+
 	var superImageSubpartitions []string
 	partitionNameProps := &filesystem.SuperImagePartitionNameProperties{}
 	if android.InList("system", partitions) {