Add support for auto-generated characteristics RRO

Setting Generate_product_characteristics_rro will automatically generate
an RRO package which contains resources with
'product="{PRODUCT_CHARACTERISTICS}"'. The RRO package will be installed
to /product partition. The app will be compiled with '--product
default', making the app identical to all targets.

Motivation for this change is to minimize divergence of system.img.

Bug: 294799593
Test: boot and idmap2 dump
Change-Id: I1371f7410a1ecf337e1f73214b024af39aa6d57a
diff --git a/java/aar.go b/java/aar.go
index 6b89129..e579008 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -102,6 +102,9 @@
 
 	// true if RRO is enforced for any of the dependent modules
 	RROEnforcedForDependent bool `blueprint:"mutated"`
+
+	// Filter only specified product and ignore other products
+	Filter_product *string `blueprint:"mutated"`
 }
 
 type aapt struct {
@@ -162,6 +165,10 @@
 	return BoolDefault(a.aaptProperties.Use_resource_processor, false)
 }
 
+func (a *aapt) filterProduct() string {
+	return String(a.aaptProperties.Filter_product)
+}
+
 func (a *aapt) ExportPackage() android.Path {
 	return a.exportPackage
 }
@@ -432,7 +439,7 @@
 	var compiledResDirs []android.Paths
 	for _, dir := range resDirs {
 		a.resourceFiles = append(a.resourceFiles, dir.files...)
-		compiledResDirs = append(compiledResDirs, aapt2Compile(ctx, dir.dir, dir.files, compileFlags).Paths())
+		compiledResDirs = append(compiledResDirs, aapt2Compile(ctx, dir.dir, dir.files, compileFlags, a.filterProduct()).Paths())
 	}
 
 	for i, zip := range resZips {
@@ -491,7 +498,7 @@
 	}
 
 	for _, dir := range overlayDirs {
-		compiledOverlay = append(compiledOverlay, aapt2Compile(ctx, dir.dir, dir.files, compileFlags).Paths()...)
+		compiledOverlay = append(compiledOverlay, aapt2Compile(ctx, dir.dir, dir.files, compileFlags, a.filterProduct()).Paths()...)
 	}
 
 	var splitPackages android.WritablePaths