Allow for reproducible builds

REPRODUCIBLE_BUILD=1 ./gradlew clean :build

gradle/reprod/patches/mixin/0001-Configure-gradle-to-build-reproducible-archives.patch

@@ -0,0 +1,28 @@
+From e60dd702c247692529a7cece94a475650623482e Mon Sep 17 00:00:00 2001
+From: Jonas Herzig <me@johni0702.de>
+Date: Tue, 8 Aug 2017 19:05:14 +0200
+Subject: [PATCH 1/7] Configure gradle to build reproducible archives
+
+---
+ build.gradle | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/build.gradle b/build.gradle
+index 4f0aa28..e0c46ea 100644
+--- a/build.gradle
++++ b/build.gradle
+@@ -170,6 +170,11 @@ processResources {
+    from 'LICENSE.txt'
+ }
+ 
++tasks.withType(AbstractArchiveTask) {
++    preserveFileTimestamps = false
++    reproducibleFileOrder = true
++}
++
+ // License header formatting
+ license {
+     ext {
+-- 
+2.5.5
+