I just tried it in 6.2.7.3753. It definitely is not working. There's no "dir" output in the Console or Output or C Output tools. No Windows command window popped up. Nothing at all happened; C compilation just completed normally.

What steps did you do to make it work? I compiled by selecting the Project | Compile menu. Looking at my .ecf file, it has this:

<post_compile_action command="cmd /c &quot;dir &amp;&amp; pause&quot;">
</post_compile_action>