title: How to get automake to set libdir to /usr/lib64 on dual-arch Linux platforms
body: <p>I'm maintaining an autotools-configured project, and I've noticed in a plain autotool setup:</p>
  
  <pre><code>libtoolize --verbose --copy --force
  aclocal --verbose -I m4 -Wall
  autoheader -Wall --verbose
  autoconf -Wall --verbose
  automake --add-missing --force-missing --copy --warnings=override -Wall
  ./configure --prefix=/usr
  make 
  make install
  Installing libexample.so in /usr/lib
  </code></pre>
  
  <p>that the make install resulting from my build (on x86_64 arch, linux) puts
  generated libraries in <code>$prefix/lib</code>.</p>
  
  <p>I was expecting the library(s) to have an <code>$LIBDIR</code> set to <code>$prefix/lib64</code>.</p>
  
  <ul>
  <li>Is there something I should do differently, or </li>
  <li>is there a 'secret' m4 macro to automatically determine this, or</li>
  <li>is the the expected behavior?</li>
  </ul>