Update script to build and upload MiniBench artifacts

Build this app during CI. We can start trying it with
```
adb shell am start -n org.pytorch.minibench/org.pytorch.minibench.BenchmarkActivity --es model_path /data/local/tmp/model.pte
adb shell run-as org.pytorch.minibench cat files/benchmark_results.txt
```

Pull Request resolved: #5017

Author: kirklandsign

build/build_android_llm_demo.sh

@@ -91,12 +91,18 @@ build_aar() {
   popd
 }
 
-build_android_llm_demo_app() {
+build_android_demo_apps() {
   mkdir -p examples/demo-apps/android/LlamaDemo/app/libs
   cp ${BUILD_AAR_DIR}/executorch-llama.aar examples/demo-apps/android/LlamaDemo/app/libs
   pushd examples/demo-apps/android/LlamaDemo
   ANDROID_HOME="${ANDROID_SDK:-/opt/android/sdk}" ./gradlew build assembleAndroidTest
   popd
+
+  mkdir -p extension/android/benchmark/app/libs
+  cp ${BUILD_AAR_DIR}/executorch.aar extension/android/benchmark/app/libs
+  pushd extension/android/benchmark
+  ANDROID_HOME="${ANDROID_SDK:-/opt/android/sdk}" ./gradlew build
+  popd
 }
 
 collect_artifacts_to_be_uploaded() {
@@ -116,6 +122,10 @@ collect_artifacts_to_be_uploaded() {
   # Collect JAR and AAR
   cp extension/android/build/libs/executorch.jar "${DEMO_APP_DIR}"
   find "${BUILD_AAR_DIR}/" -name 'executorch*.aar' -exec cp {} "${DEMO_APP_DIR}" \;
+  # Collect MiniBench APK
+  MINIBENCH_APP_DIR="${ARTIFACTS_DIR_NAME}/minibench"
+  mkdir -p "${MINIBENCH_APP_DIR}"
+  cp extension/android/benchmark/app/build/outputs/apk/debug/*.apk "${MINIBENCH_APP_DIR}"
 }
 
 BUILD_AAR_DIR="$(mktemp -d)"
@@ -130,5 +140,5 @@ for ANDROID_ABI in "${ANDROID_ABIS[@]}"; do
   build_android_native_library ${ANDROID_ABI}
 done
 build_aar
-build_android_llm_demo_app
+build_android_demo_apps
 collect_artifacts_to_be_uploaded ${ARTIFACTS_DIR_NAME}