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/AaptAssets.cpp b/tools/aapt/AaptAssets.cpp
index b94d14f..0fc2617 100644
--- a/tools/aapt/AaptAssets.cpp
+++ b/tools/aapt/AaptAssets.cpp
@@ -1540,7 +1540,7 @@
     }
 
     const String8& featureOfBase = bundle->getFeatureOfPackage();
-    if (!featureOfBase.isEmpty()) {
+    if (!featureOfBase.empty()) {
         if (bundle->getVerbose()) {
             printf("Including base feature resources from package: %s\n",
                     featureOfBase.c_str());