title: GNU Make: how to join list and separate it with separator?
body: <p>I have this:</p>
  
  <pre><code>FOO = foo1 foo2 ... fooN
  </code></pre>
  
  <p>and want to get join all these string and separate it with, for instance, colong:</p>
  
  <pre><code>foo1:foo2:foo3:...:fooN
  </code></pre>
  
  <p>How to do this in GNU Make, without using external UNIX tools?</p>