fix shellcheck errors in 2018/burton2/runtest.sh

2018/burton2/runtest.sh

@@ -1,9 +1,9 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
-: ${prog:=./prog}
+: "${prog:=./prog}"
-: ${opt:=crs}
+: "${opt:=crs}"
 
 exec 2>&1
 for name in test*c fixed_iocccsize.c ioc_without_quote; do
-	/bin/echo -n "$name: "; $prog -$opt < $name
+	/bin/echo -n "$name: "; "$prog" -"$opt" < "$name"
 done