Update build.gradle

Load Android Gradle Plugin conditionally

Author: SaeedZhiany

android/build.gradle

@@ -1,15 +1,20 @@
 apply plugin: 'com.android.library'
 
 buildscript {
-  repositories {
-    maven { url "https://maven.google.com" }
-    jcenter()
-    google()
-  }
+    // The Android Gradle plugin is only required when opening the android folder stand-alone.
+    // This avoids unnecessary downloads and potential conflicts when the library is included as a
+    // module dependency in an application project.
+    if (project == rootProject) {
+        repositories {
+            maven { url "https://maven.google.com" }
+            jcenter()
+            google()
+        }
 
-  dependencies {
-    classpath 'com.android.tools.build:gradle:3.4.1'
-  }
+        dependencies {
+            classpath 'com.android.tools.build:gradle:3.5.1'
+        }
+    }
 }
 
 def safeExtGet(prop, fallback) {