unix: Properly cancel REPL input when Ctrl-C is pressed.

unix/main.c

@@ -176,7 +176,11 @@ STATIC int do_repl(void) {
         int ret = readline(&line, ">>> ");
         mp_parse_input_kind_t parse_input_kind = MP_PARSE_SINGLE_INPUT;
 
-        if (ret == CHAR_CTRL_D) {
+        if (ret == CHAR_CTRL_C) {
+            // cancel input
+            mp_hal_stdout_tx_str("\r\n");
+            goto input_restart;
+        } else if (ret == CHAR_CTRL_D) {
             // EOF
             printf("\n");
             mp_hal_stdio_mode_orig();