Fix gradle

Author: kirklandsign

examples/demo-apps/android/LlamaDemo/app/build.gradle.kts

@@ -11,7 +11,8 @@ plugins {
   id("org.jetbrains.kotlin.android")
 }
 
-def qnnVersion = System.properties['qnnVersion']
+val qnnVersion: String? = project.findProperty("qnnVersion") as? String
+
 
 android {
   namespace = "com.example.executorchllamademo"
@@ -63,8 +64,8 @@ dependencies {
   implementation("com.google.android.material:material:1.12.0")
   implementation("androidx.activity:activity:1.9.0")
   implementation("org.json:json:20250107")
-  if (qnnVersion) {
-    implementation "com.qualcomm.qti:qnn-runtime:$qnnVersion"
+  if (!qnnVersion.isNullOrEmpty()) {
+    implementation("com.qualcomm.qti:qnn-runtime:$qnnVersion")
   }
   testImplementation("junit:junit:4.13.2")
   androidTestImplementation("androidx.test.ext:junit:1.1.5")