Migrate from android::String isEmpty to empty [aapt]

This empty method is different from the old one - it aligns with
std::string definition.

Bug: 295394788
Test: make checkbuild
Change-Id: I1900f2285ee3c3b1eb57d2cef3990896a64dae01
Merged-In: I1900f2285ee3c3b1eb57d2cef3990896a64dae01
diff --git a/tools/aapt/Resource.cpp b/tools/aapt/Resource.cpp
index 9c944e0..4a360ed 100644
--- a/tools/aapt/Resource.cpp
+++ b/tools/aapt/Resource.cpp
@@ -1285,7 +1285,7 @@
         packageType = ResourceTable::SharedLibrary;
     } else if (bundle->getExtending()) {
         packageType = ResourceTable::System;
-    } else if (!bundle->getFeatureOfPackage().isEmpty()) {
+    } else if (!bundle->getFeatureOfPackage().empty()) {
         packageType = ResourceTable::AppFeature;
     }
 
@@ -3144,7 +3144,7 @@
 
     tree.restart();
 
-    if (!startTags.isEmpty()) {
+    if (!startTags.empty()) {
         bool haveStart = false;
         while ((code=tree.next()) != ResXMLTree::END_DOCUMENT && code != ResXMLTree::BAD_DOCUMENT) {
             if (code != ResXMLTree::START_TAG) {