title: Can't get R to recognize installed libgfortran when installing packages
body: <p>I'm trying to install packages in R that depend on libgfortran, but I keep getting this error:</p>
  
  <pre><code>dyld: Library not loaded: /usr/local/opt/gcc/lib/gcc/7/libgfortran.4.dylib
    Referenced from: /usr/local/Cellar/r/3.4.3_1/lib/libR.dylib
    Reason: image not found
  </code></pre>
  
  <p>I have gfortran installed through homebrew gcc:</p>
  
  <pre><code> ❯❯ readlink `which gfortran`
  ../Cellar/gcc/8.2.0/bin/gfortran
  </code></pre>
  
  <p>There's a libgfortran available at <code>/usr/local/opt/gcc/lib/gcc/8/libgfortran.5.dylib</code>, but this is not the one R is looking for. How do I convince R to look for gcc 8 instead of gcc 7?</p>