`ls`: fix output on prompts without newline at beginning.

i *swore* i fixed this (and i did for other programs) but i guess this one just escaped my mind.
very sad.

src/ls.c

@@ -167,5 +167,6 @@ int main(int argc, char** argv) {
 		}
 	}
 	free(out);
+	printf("\n");
 	return 0;
 }