title: Make GNU: get letter/char from variable
body: <p>I have a variable in a GNU make file :</p>
  
  <pre><code>VAR=DDC
  </code></pre>
  
  <p>I want to merge these characters into another string and assign them to a different variable, for example: </p>
  
  <pre><code>TOT_VAR=--'D','D','C'--
  </code></pre>
  
  <p>My first idea was to do something like this pseudocode: </p>
  
  <pre><code>#Pseudo code
  TOT_VAR=--'@(letter1, VAR)','@(letter2, VAR)','@(letter3, VAR)'--
  </code></pre>
  
  <p>But I can't find any function that extracts individual characters.
  How might I do this?</p>