Fix Windows build

Makefile

@@ -104,15 +104,9 @@ endif
 # ----------
 
 # Cleanup
-ifeq ($(OSTYPE), Windows)
-clean:
-	@echo "===> CLEAN"
-	@-rmdir /S /Q release build
-else
 clean:
 	@echo "===> CLEAN"
 	${Q}rm -Rf build release
-endif
 
 # ----------
 
@@ -120,12 +114,12 @@ endif
 ifeq ($(OSTYPE), Windows)
 zaero:
 	@echo "===> Building game.dll"
-	${Q}tools/mkdir.exe -p release
+	${Q}mkdir -p release
 	${MAKE} release/game.dll
 
 build/%.o: %.c
 	@echo "===> CC $<"
-	${Q}tools/mkdir.exe -p $(@D)
+	${Q}mkdir -p $(@D)
 	${Q}$(CC) -c $(CFLAGS) -o $@ $<
 else
 zaero: