Switch to aapt2 for getting minSdkVersion

aapt does not support parsing some referencing attributes.
Switch to latest tool, aapt2, which works better.

Test: aapt2 dump badging test.apk and returned 0.
Test: Run check_target_files_signatures.py with a target_files.zip.
Test: Run sign_target_files_apks.py with a target_files.zip.
Change-Id: Ib3a4740506f29ebab6930767f2aa8a0b5c4ba053
diff --git a/tools/releasetools/Android.bp b/tools/releasetools/Android.bp
index d4c4673..65eee94 100644
--- a/tools/releasetools/Android.bp
+++ b/tools/releasetools/Android.bp
@@ -37,7 +37,7 @@
     // Only the tools that are referenced directly are listed as required modules. For example,
     // `avbtool` is not here, as the script always uses the one from info_dict['avb_avbtool'].
     required: [
-        "aapt",
+        "aapt2",
         "boot_signer",
         "brotli",
         "bsdiff",