Build AAR in release/0.2 branch (#3820)

* Rename so file to match soname (#3810)

Summary: Pull Request resolved: #3810

Test Plan: Use artifact from https://gha-artifacts.s3.amazonaws.com/pytorch/executorch/9356134478/artifact/executorch-llama.aar to build demo app

Reviewed By: shoumikhin

Differential Revision: D58100605

Pulled By: kirklandsign

fbshipit-source-id: a1febda12a546b7bf53c1059a603fece0e5553c5
(cherry picked from commit 2c00ade)

* Need to build aar in release branch as well

Author: kirklandsign

build/test_android_ci.sh

@@ -22,6 +22,7 @@ build_android_native_library() {
   pushd examples/demo-apps/android/LlamaDemo
   CMAKE_OUT="cmake-out-android-$1" ANDROID_NDK=/opt/ndk ANDROID_ABI="$1" ./gradlew setup
   popd
+  cp "cmake-out-android-$1"/extension/android/*.so build_aar/jni/$1/
 }
 
 build_android_demo_app() {
@@ -37,8 +38,27 @@ build_android_llama_demo_app() {
   popd
 }
 
+build_aar() {
+  cp extension/android/build/libs/executorch.jar build_aar/libs
+  echo \<manifest xmlns:android=\"http://schemas.android.com/apk/res/android\" \
+   package=\"org.pytorch.executorch\"\> \
+   \<uses-sdk android:minSdkVersion=\"19\" /\> \
+   \</manifest\> > build_aar/AndroidManifest.xml
+  pushd build_aar
+  mv jni/arm64-v8a/libexecutorch_jni.so jni/arm64-v8a/libexecutorch.so
+  mv jni/x86_64/libexecutorch_jni.so jni/x86_64/libexecutorch.so
+  zip -r executorch.aar libs jni AndroidManifest.xml
+
+  rm jni/arm64-v8a/libexecutorch.so jni/x86_64/libexecutorch.so
+  zip -r executorch-llama.aar libs jni AndroidManifest.xml
+  popd
+}
+
+mkdir -p build_aar/jni/arm64-v8a build_aar/jni/x86_64 build_aar/libs
+
 build_android_native_library arm64-v8a
 build_android_native_library x86_64
 export_model
 build_android_demo_app
 build_android_llama_demo_app
+build_aar