Use a.out as standard output file

app/mc_asm.c

@@ -122,7 +122,7 @@ int main(int argc, char *argv[]) {
     mcc_asm_gen_creator(out, tac, symbol_table);
 	fclose(as_file);
 
-    mcc_invoke_gcc(TMP_FILE_NAME".s", out);
+    mcc_invoke_gcc(TMP_FILE_NAME".s", "a.out");
 
     // mcc_asm_gen_creator(stdout, tac, symbol_table);