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

Makefile

@@ -0,0 +1,30 @@
+RUN_ENGINE?=engine/build/gzdoom
+BUILD_ENGINE=$(RUN_ENGINE)
+RM=rm -rf
+
+ifeq ($(OS),Windows_NT)
+	RUN_ENGINE=gzdoom
+	BUILD_ENGINE=""
+	RM=del
+endif
+
+all: $(BUILD_ENGINE)
+
+clean: clean-zmusic clean-engine
+
+# GZDoom engine build. Only relevant for GNU/Linux
+clean-zmusic:
+	$(MAKE) -C ZMusic/build clean
+	$(RM) ZMusic/build
+
+clean-engine:
+	$(MAKE) -C engine/build clean
+	$(RM) engine/build
+
+ZMusic/build:
+	cd ZMusic && mkdir -p build && cd build && cmake ..
+	$(MAKE) -C ZMusic/build
+
+engine/build/gzdoom: ZMusic/build
+	cd engine && mkdir -p build && cd build && cmake --verbose=1 -DZMUSIC_LIBRARIES=../../ZMusic/build/source/libzmusic.so -DZMUSIC_INCLUDE_DIR=../../ZMusic/include ..
+	$(MAKE) -C engine/build