title: Can't compile C program on a Mac after upgrade to Mojave
body: <p>I have used the gcc command on the terminal to compile C programs but all of a sudden, after an update to my Mac's OS (to macOS 10.14 Mojave, and XCode 10.0), I started receiving the message:</p>
  
  <pre><code>test.c:8:10: fatal error: stdio.h: No such file or directory
  #include &lt;stdio.h&gt;
           ^~~~~~~~~
  compilation terminated.
  </code></pre>
  
  <p>I already have gcc installed as I can find it in <code>/usr/local/bin</code> and there really is a gcc in there. I tried running the same file on my other iMac and it worked without any issue. </p>
  
  <p>I tried running <code>xcode-select --install</code> and it already was installed, hence it didn't fix the issue I'm having now. I'm guessing that the path is messed up as it doesn't seem like it can find <code>gcc</code> after I started copying and pasting some commands from other resources to solve this issue.</p>
  
  <p>Would like some help on this.</p>