Create super_empty.img using Soong

The build rule for this .img file will be created in super_image. It
will use the a minimized file returned by `buildMiscInfo` without any
partition information. This file will be disted in target_files.zip

Bug: 390192334
Test: Verified that this file is bit-identical between make and soong
for aosp_cf_x86_64_phone

Change-Id: I9238d67d2ca8739064509a858d5251f2641896e9
diff --git a/fsgen/super_img.go b/fsgen/super_img.go
index f564636..1d610f6 100644
--- a/fsgen/super_img.go
+++ b/fsgen/super_img.go
@@ -46,6 +46,7 @@
 		Retrofit:                      proptools.BoolPtr(partitionVars.ProductRetrofitDynamicPartitions),
 		Use_dynamic_partitions:        proptools.BoolPtr(partitionVars.ProductUseDynamicPartitions),
 		Super_image_in_update_package: proptools.BoolPtr(partitionVars.BoardSuperImageInUpdatePackage),
+		Create_super_empty:            proptools.BoolPtr(partitionVars.BuildingSuperEmptyImage),
 	}
 	if partitionVars.ProductVirtualAbOta {
 		superImageProps.Virtual_ab.Enable = proptools.BoolPtr(true)