title: string_view not found when compiling c++17 code with clang in Ubuntu
body: <p>I got the error message:</p>
  
  <pre><code>src/HttpRouter.h:28:10: fatal error: 'string_view' file not found
  </code></pre>
  
  <p>when trying to compile a library (uWebSockets) which happened to show the command it called to compile:</p>
  
  <pre><code>clang++ -flto -O3 -c -std=c++17 -Isrc -IuSockets/src examples/HelloWorld.cpp
  </code></pre>
  
  <p>I checked /usr/include and <code>string_view</code> was only found inside <code>experimental</code></p>
  
  <pre><code>john@blam /usr/include $ find . | grep string_view
    ./c++/5/experimental/string_view.tcc
    ./c++/5/experimental/string_view
  </code></pre>
  
  <p>Even after I updated to libstdc++6-dev, it still can't find string_view library which came from the <code>#include &lt;string_view&gt;</code> line.</p>
  
  <p>What gives?</p>