Split out nukage engine build into separate project for if/when we want to actually use it.

.drone.yml

@@ -0,0 +1,11 @@
+pipeline:
+  build-environment:
+    image: docker
+    commands:
+      - cat Dockerfile | docker build -t nukage-ci -
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock     
+  build-engine:
+    image: nukage-ci
+    commands:
+      - make engine/build/gzdoom