Update build.gradle

build.gradle

@@ -3,16 +3,17 @@ import org.signal.signing.ApkSignerUtil
 import java.security.MessageDigest
 
 buildscript {
-    ext.kotlin_version = '1.3.31'
+    ext.gradle_version = "3.4.1"
+    ext.kotlin_version = "1.3.31"
     repositories {
         google()
+        mavenCentral()
         maven {
             url "https://repo1.maven.org/maven2"
         }
-        mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.4.1'
+        classpath "com.android.tools.build:gradle:$gradle_version"
         classpath files('libs/gradle-witness.jar')
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }