mindustry: build Arc from source (#108274)

- reduce the buildPhase of the fixed-output dependencies derivation to
  only download all dependencies, instead of building the full thing.
- add wayland variant, which is linked against a different variant of
  the glew library to run natively using SDL_VIDEODRIVER=wayland
- use jdk (Java 15) instead of jre (Java 8) at runtime
- use new copyDesktopItems hook

pkgs/games/mindustry/0001-fix-include-path-for-SDL2-on-linux.patch

@@ -0,0 +1,33 @@
+From 9dbfa680db6bfd1033772dda753120fe4452e0d9 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Milan=20P=C3=A4ssler?= <milan@petabyte.dev>
+Date: Fri, 8 Jan 2021 04:49:14 +0100
+Subject: [PATCH] fix include path for SDL2 on linux
+
+---
+ .../src/main/java/arc/backend/sdl/jni/SDL.java            | 8 --------
+ 1 file changed, 8 deletions(-)
+
+diff --git a/backends/backend-sdl/src/main/java/arc/backend/sdl/jni/SDL.java b/backends/backend-sdl/src/main/java/arc/backend/sdl/jni/SDL.java
+index 62d9286a..2853119d 100644
+--- a/Arc/backends/backend-sdl/src/main/java/arc/backend/sdl/jni/SDL.java
++++ b/Arc/backends/backend-sdl/src/main/java/arc/backend/sdl/jni/SDL.java
+@@ -8,16 +8,8 @@ import java.nio.*;
+ public class SDL{
+     /*JNI
+ 
+-    #ifdef __APPLE__
+-
+     #include "SDL2/SDL.h"
+ 
+-    #else
+-
+-    #include "SDL.h"
+-
+-    #endif
+-
+     */
+ 
+     static{
+-- 
+2.29.2
+