Android add notes about using local AAR (#90)

Add an option to use local AAR

Author: kirklandsign

llm/android/LlamaDemo/README.md

@@ -30,7 +30,7 @@ First it’s important to note that by default, the app depends on [ExecuTorch l
 
 No modification is needed if you want to use the default ExecuTorch library.
 
-However, you can build your own ExecuTorch Android library (an AAR file). In app/build.gradle.kts file, replace `org.pytorch:executorch-android:x.y.z` with `files("path-to-aar")`.
+However, you can build your own ExecuTorch Android library (an AAR file). Copy the file to app/libs/executorch.aar. In gradle.properties file, add a line `useLocalAar=true` so that gradle uses that file.
 
 [This page](https://github.com/pytorch/executorch/blob/main/extension/android/README.md) contains the documentation for building the ExecuTorch Android library.
 

llm/android/LlamaDemo/app/build.gradle.kts

@@ -12,6 +12,7 @@ plugins {
 }
 
 val qnnVersion: String? = project.findProperty("qnnVersion") as? String
+val useLocalAar: Boolean? = (project.findProperty("useLocalAar") as? String)?.toBoolean()
 
 android {
   namespace = "com.example.executorchllamademo"
@@ -59,7 +60,11 @@ dependencies {
   implementation("androidx.constraintlayout:constraintlayout:2.2.0-alpha12")
   implementation("com.facebook.fbjni:fbjni:0.5.1")
   implementation("com.google.code.gson:gson:2.8.6")
-  implementation("org.pytorch:executorch-android:1.0.0-rc1")
+  if (useLocalAar == true) {
+    implementation(files("libs/executorch.aar"))
+  } else {
+    implementation("org.pytorch:executorch-android:1.0.0-rc1")
+  }
   implementation("com.google.android.material:material:1.12.0")
   implementation("androidx.activity:activity:1.9.0")
   implementation("org.json:json:20250107")