chore: avoid config overwrite

Makefile

@@ -59,7 +59,7 @@ spell::
 	codespell $(wildcard *.md) docs src tests config contrib
 
 init.app::
-	cp config/sample.engine-core.ini config/engine-core.ini
+	cp -n config/sample.engine-core.ini config/engine-core.ini
 	mkdir -p audio/fallback
 	mkdir -p audio/playlist
 	mkdir -p audio/source