android: Update Gradle plugin

src/frontends/android/build.gradle

@@ -4,7 +4,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.3'
+        classpath 'com.android.tools.build:gradle:4.0.1'
     }
 }
 

src/frontends/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Wed Feb 26 10:22:42 CET 2020
+#Mon Oct 05 15:58:06 CEST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip