fix: specify jvm target config

Author: ovitrif

bindings/kotlin/ldk-node-android/lib/build.gradle.kts

@@ -33,6 +33,15 @@ android {
         }
     }
 
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_1_8
+        targetCompatibility = JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
+
     publishing {
         singleVariant("release") {
             withSourcesJar()