Remove redundant "unknown option" error messages (#1441)

`getopt` already prints "unrecognized option"

src/asm/main.cpp

@@ -281,7 +281,6 @@ int main(int argc, char *argv[]) {
 
 		// Unrecognized options
 		default:
-			fprintf(stderr, "FATAL: unknown option '%c'\n", ch);
 			printUsage();
 			exit(1);
 		}