Update build scripts

run

@@ -1,3 +1,23 @@
 #!/bin/bash
 
-./build_dir/main
+USAGE="Usage: run (raytracer | rasteriser)"
+
+if [[ $# == 0 ]]; then
+	echo $USAGE
+	exit 1
+fi
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    raytracer)
+      RENDERER="raytracer"
+      shift # past argument
+      ;;
+    -*|--*|*)
+			echo $USAGE
+      exit 1
+      ;;
+  esac
+done
+
+./build_dir/$RENDERER