Fix checking for subdirs when parsing apks

This fixes the check for subdirectories in lib paths. The old check
caused a crash.

Test: Automated
Fixes: 268582810
Change-Id: I520f1fd6772b11821e7c5c97bd51b45b603f5a7b
diff --git a/libs/androidfw/ApkParsing.cpp b/libs/androidfw/ApkParsing.cpp
index cf4fbb9..32d2c5b 100644
--- a/libs/androidfw/ApkParsing.cpp
+++ b/libs/androidfw/ApkParsing.cpp
@@ -56,10 +56,8 @@
         return nullptr;
     }
 
-    // Make sure there aren't subdirectories
-    const char* abiOffset = fileName + APK_LIB_LEN;
-    const size_t abiSize = lastSlash - abiOffset;
-    if (memchr(abiOffset, '/', abiSize)) {
+    // Make sure there aren't subdirectories by checking if the next / after lib/ is the last slash
+    if (memchr(fileName + APK_LIB_LEN, '/', fileNameLen - APK_LIB_LEN) != lastSlash) {
         return nullptr;
     }