Add microdroid demo app

Add a demo app showing how an app can start a VM.

Bug: N/A
Test: TARGET_BUILD_APPS=MicrodroidDemoApp m apps_only dist
adb install out/dist/MicrodroidDemoApp.apk
adb push out/dist/MicrodroidDemoApp.apk.idsig /data/local/tmp/virt/
adb root
adb shell start virtualizationservice
<then launch the app>

Change-Id: If46b2f8910b98b2b29ca0c629e1f7eacc01a477a
diff --git a/demo/Android.bp b/demo/Android.bp
new file mode 100644
index 0000000..77049de
--- /dev/null
+++ b/demo/Android.bp
@@ -0,0 +1,21 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+android_app {
+    name: "MicrodroidDemoApp",
+    srcs: ["java/**/*.java"],
+    resource_dirs: ["res"],
+    static_libs: [
+        "androidx-constraintlayout_constraintlayout",
+        "androidx.appcompat_appcompat",
+        "com.google.android.material_material",
+    ],
+    libs: [
+        "android.system.virtualmachine",
+    ],
+    jni_libs: ["MicrodroidTestNativeLib"],
+    platform_apis: true,
+    use_embedded_native_libs: true,
+    v4_signature: true,
+}