fix: get gradle version dynamically

Author: szymonrybczak

packages/create-react-native-library/templates/native-common/android/build.gradle

@@ -1,16 +1,18 @@
 buildscript {
   // Buildscript is evaluated before everything else so we can't use getExtOrDefault
-  def kotlin_version = rootProject.ext.has("kotlinVersion") ? rootProject.ext.get("kotlinVersion") : project.properties["<%- project.name -%>_kotlinVersion"]
+  ext.getExtOrDefault = {name ->
+    return rootProject.ext.has(name) ? rootProject.ext.get(name) : project.properties['<%- project.name -%>_' + name]
+  }
 
   repositories {
     google()
     mavenCentral()
   }
 
   dependencies {
-    classpath "com.android.tools.build:gradle:7.2.1"
+    classpath "com.android.tools.build:gradle:${getExtOrDefault('gradleVersion')}"
     // noinspection DifferentKotlinGradleVersion
-    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:${getExtOrDefault('kotlinVersion')}"
   }
 }