title: gnu make: How to concat two strings
body: <p>Given the line:</p>
  
  <pre><code>program_OBJS := ${program_SRCS:.cpp=.o}
  </code></pre>
  
  <p>I would like to append <code>.o</code> to each filename instead of replacing <code>.cpp</code> with <code>.o</code>.</p>
  
  <p>How do I do that?</p>