title: Makefile don't check dependency timestamps
body: <p>I am writing a makefile like this</p>
  
  <pre><code>foo: bar
      touch foo
  </code></pre>
  
  <p>but I want <code>foo</code> to be built <em>only</em> if it's missing, regardless of whether <code>bar</code> is newer than <code>foo</code>. Is that possible with make? </p>