Add rules to handle asset resources.

AAPT2 ignores assets in overlay resource inputs, so separate rules are
required to extract and merge assets from dependencies.

Test: app_test.go
Test: Added assets to Settings-core for testing
Test: Confirmed Settings.apk contains them with this change.
Fixes: 146655310
Change-Id: Iab8bc61b719541dae64f0e3502bc9cb45a353687
diff --git a/android/util.go b/android/util.go
index 81f481d..e985fc1 100644
--- a/android/util.go
+++ b/android/util.go
@@ -121,8 +121,19 @@
 	return IndexList(s, list) != -1
 }
 
-func PrefixInList(s string, list []string) bool {
-	for _, prefix := range list {
+// Returns true if the given string s is prefixed with any string in the given prefix list.
+func PrefixInList(s string, prefixList []string) bool {
+	for _, prefix := range prefixList {
+		if strings.HasPrefix(s, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+// Returns true if any string in the given list has the given prefix.
+func PrefixedStringInList(list []string, prefix string) bool {
+	for _, s := range list {
 		if strings.HasPrefix(s, prefix) {
 			return true
 		}