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/android/variable.go b/android/variable.go
index 853d8ef..2134763 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -654,6 +654,7 @@
 	ProductUseDynamicPartitions       bool                                     `json:",omitempty"`
 	ProductRetrofitDynamicPartitions  bool                                     `json:",omitempty"`
 	ProductBuildSuperPartition        bool                                     `json:",omitempty"`
+	BuildingSuperEmptyImage           bool                                     `json:",omitempty"`
 	BoardSuperPartitionSize           string                                   `json:",omitempty"`
 	BoardSuperPartitionMetadataDevice string                                   `json:",omitempty"`
 	BoardSuperPartitionBlockDevices   []string                                 `json:",omitempty"`
diff --git a/filesystem/android_device.go b/filesystem/android_device.go
index 22ad7cf..45a8620 100644
--- a/filesystem/android_device.go
+++ b/filesystem/android_device.go
@@ -623,6 +623,10 @@
 					builder.Command().Textf("cp ").Input(info.SubImageInfo[partition].MapFile).Textf(" %s/IMAGES/", targetFilesDir.String())
 				}
 			}
+			// super_empty.img
+			if info.SuperEmptyImage != nil {
+				builder.Command().Textf("cp ").Input(info.SuperEmptyImage).Textf(" %s/IMAGES/", targetFilesDir.String())
+			}
 		} else {
 			ctx.ModuleErrorf("Super partition %s does set SuperImageProvider\n", superPartition.Name())
 		}
diff --git a/filesystem/super_image.go b/filesystem/super_image.go
index 5108025..8e2b532 100644
--- a/filesystem/super_image.go
+++ b/filesystem/super_image.go
@@ -80,6 +80,8 @@
 	}
 	// Whether the super image will be disted in the update package
 	Super_image_in_update_package *bool
+	// Whether a super_empty.img should be created
+	Create_super_empty *bool
 }
 
 type PartitionGroupsInfo struct {
@@ -118,6 +120,8 @@
 	SubImageInfo map[string]FilesystemInfo
 
 	DynamicPartitionsInfo android.Path
+
+	SuperEmptyImage android.Path
 }
 
 var SuperImageProvider = blueprint.NewProvider[SuperImageInfo]()
@@ -163,7 +167,7 @@
 }
 
 func (s *superImage) GenerateAndroidBuildActions(ctx android.ModuleContext) {
-	miscInfo, deps, subImageInfos := s.buildMiscInfo(ctx)
+	miscInfo, deps, subImageInfos := s.buildMiscInfo(ctx, false)
 	builder := android.NewRuleBuilder(pctx, ctx)
 	output := android.PathForModuleOut(ctx, s.installFileName())
 	lpMake := ctx.Config().HostToolPath(ctx, "lpmake")
@@ -176,10 +180,27 @@
 		Implicits(deps).
 		Output(output)
 	builder.Build("build_super_image", fmt.Sprintf("Creating super image %s", s.BaseModuleName()))
+	var superEmptyImage android.WritablePath
+	if proptools.Bool(s.properties.Create_super_empty) {
+		superEmptyImageBuilder := android.NewRuleBuilder(pctx, ctx)
+		superEmptyImage = android.PathForModuleOut(ctx, "super_empty.img")
+		superEmptyMiscInfo, superEmptyDeps, _ := s.buildMiscInfo(ctx, true)
+		if superEmptyDeps != nil {
+			ctx.ModuleErrorf("TODO: Handle additional deps when building super_empty.img")
+		}
+		superEmptyImageBuilder.Command().Textf("PATH=%s:\\$PATH", lpMakeDir).
+			BuiltTool("build_super_image").
+			Text("-v").
+			Input(superEmptyMiscInfo).
+			Implicit(lpMake).
+			Output(superEmptyImage)
+		superEmptyImageBuilder.Build("build_super_empty_image", fmt.Sprintf("Creating super empty image %s", s.BaseModuleName()))
+	}
 	android.SetProvider(ctx, SuperImageProvider, SuperImageInfo{
 		SuperImage:            output,
 		SubImageInfo:          subImageInfos,
 		DynamicPartitionsInfo: s.generateDynamicPartitionsInfo(ctx),
+		SuperEmptyImage:       superEmptyImage,
 	})
 	ctx.SetOutputFiles([]android.Path{output}, "")
 	ctx.CheckbuildFile(output)
@@ -191,7 +212,7 @@
 	return "super.img"
 }
 
-func (s *superImage) buildMiscInfo(ctx android.ModuleContext) (android.Path, android.Paths, map[string]FilesystemInfo) {
+func (s *superImage) buildMiscInfo(ctx android.ModuleContext, superEmpty bool) (android.Path, android.Paths, map[string]FilesystemInfo) {
 	var miscInfoString strings.Builder
 	partitionList := s.dumpDynamicPartitionInfo(ctx, &miscInfoString)
 	addStr := func(name string, value string) {
@@ -201,6 +222,11 @@
 		miscInfoString.WriteRune('\n')
 	}
 	addStr("ab_update", strconv.FormatBool(proptools.Bool(s.properties.Ab_update)))
+	if superEmpty {
+		miscInfo := android.PathForModuleOut(ctx, "misc_info_super_empty.txt")
+		android.WriteFileRule(ctx, miscInfo, miscInfoString.String())
+		return miscInfo, nil, nil
+	}
 
 	subImageInfo := make(map[string]FilesystemInfo)
 	var deps android.Paths
@@ -300,6 +326,9 @@
 	}
 
 	addStr("build_super_partition", "true")
+	if proptools.Bool(s.properties.Create_super_empty) {
+		addStr("build_super_empty_partition", "true")
+	}
 	addStr("use_dynamic_partitions", strconv.FormatBool(proptools.Bool(s.properties.Use_dynamic_partitions)))
 	if proptools.Bool(s.properties.Retrofit) {
 		addStr("dynamic_partition_retrofit", "true")
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)