android: Update Gradle plugin

src/frontends/android/build.gradle

@@ -4,7 +4,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.3.2'
+        classpath 'com.android.tools.build:gradle:3.4.2'
     }
 }
 

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

@@ -1,6 +1,6 @@
-#Mon Mar 04 17:15:25 CET 2019
+#Tue Aug 13 13:47:52 CEST 2019
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.1.1-all.zip