Update Studio, use Kotlin JDK8

build.gradle

@@ -3,14 +3,10 @@ buildscript {
     ext.kotlin_version = '1.3.72'
     repositories {
         jcenter()
-        maven {
-            url 'https://maven.google.com/'
-            name 'Google'
-        }
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.3'
+        classpath 'com.android.tools.build:gradle:4.0.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
@@ -22,3 +18,7 @@ allprojects {
         maven { url "https://jitpack.io" }
     }
 }
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}