title: Homebrew cannot find gcc
body: <p>I'm having trouble getting homebrew to work on Lion.  For some reason, it is picking up clang rather than gcc.</p>
  
  <pre><code>==&gt; Upgrading gnutls
  ...
  checking for gcc...
  /usr/bin/clang checking whether the C compiler works... no
  </code></pre>
  
  <p>'brew doctor' says:</p>
  
  <pre><code>We couldn't detect gcc 4.2.x. Some formulae require this compiler. NOTE: Versions of XCode newer than 4.2 don't include gcc 4.2.x.
  </code></pre>
  
  <p>NOTE: I have already installed command line tools from XCode, including gcc.</p>
  
  <pre><code>$ which gcc
  /usr/bin/gcc
  $ gcc -v
  gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.9.00)
  </code></pre>
  
  <p>How can I force brew to use gcc?</p>