title: Compiler fails to search "/usr/local/include" after updating to macOS Mojave
body: <p>After updating to macOS Mojave, the the OS fails to search for headers in <code>/usr/local/include</code> when compiling with <code>clang++</code> (<em>from the command-line, i.e. outside Xcode</em>). Note that <code>/usr/local/include</code> is for my system the default paths in which CMake installs the headers, it thus feels quite strange of having to manually include this. </p>
  
  <p>Incidentally I have also performed a clean install, resulting in the same problem. In the latter I have, in the following order:</p>
  
  <ol>
  <li>Installed Xcode from the App-store.</li>
  <li>Ran <code>xcode-select --install</code>.</li>
  </ol>
  
  <p>The problem appears to be similar as in <a href="https://stackoverflow.com/q/23905661/2646505">this question</a> where it is suggested to:</p>
  
  <ul>
  <li>Run <code>xcode-select --install</code>. This obviously does not solve the problem. Insisting on this by rerunning the install command results in <code>error: command line tools are already installed</code>. </li>
  <li>Then there is <a href="https://stackoverflow.com/a/36165586/2646505">the suggestion</a> to check the output of <code>xcode-select -p</code>. It should apparently read <code>/Library/Developer/CommandLineTools</code>, not  <code>/Applications/Xcode.app/Contents/Developer</code> as in my case. The suggestion is to "delete [sic] Xcode from the Applications directory", which seems to be a bit brutal.</li>
  </ul>
  
  <p>How to solve this? </p>