Merge Reproducible Builds

This commit makes release builds reproducible. This will help folks update the app from F-Droid when it's released there.

build.gradle

@@ -24,8 +24,4 @@ allprojects {
         maven { url "https://jitpack.io" }
         jcenter()
     }
-}
-
-task clean(type: Delete) {
-    delete rootProject.buildDir
-}
+}