title: Telling Cargo to look for dynamic libraries in $CONDA_PREFIX/lib
body: <p>I'm working on a project in Rust on MacOS, with some additional C/Fortran dependencies. All my dependencies are installed in my Conda environment. Unfortunately, invoking <code>cargo test</code> yields a runtime failure, because it is unable to find <code>libfortran.3.dylib</code>:</p>
  
  <pre class="lang-none prettyprint-override"><code>$ cargo test
  ...
  dyld: Library not loaded: @rpath/libgfortran.3.dylib
    Referenced from: /Users/user1/my_project/... 
    Reason: image not found
  ...
  </code></pre>
  
  <p>Setting <code>LD_LIBRARY_PATH</code> to point to the right place removes this issue:</p>
  
  <pre class="lang-none prettyprint-override"><code>$ LD_LIBRARY_PATH=$CONDA_PREFIX/lib cargo test
  ...
  running 208 tests
  test test1 .. ok
  ...
  </code></pre>
  
  <p>Is there a way to put that information in <code>Cargo.toml</code> so I don't have to explicitly modify the environment?</p>