title: Evaluate values in dir locals
body: <p>I have a plugin system setup that will (at compile time) search through all the plugins in the plugins directory.</p>
  
  <p>My problem is that I'm trying to allow for flycheck to add these plugins' headers to the include paths.</p>
  
  <p>I have the problem that I can't figure out how to make the expression actually evaluate to its value. (The expression is treated as a value rather than being evaluated)</p>
  
  <pre><code>((c++-mode . ((flycheck-clang-include-path . (split-string (substring
                                                              (shell-command-to-string
                                                               (concat "echo src;"
                                                                       "cd /home/czipperz/vick &amp;&amp;"
                                                                       "[ \"$(ls plugins)\" ] &amp;&amp;"
                                                                       "[ \"$(find plugins -name src -type d)\" ] &amp;&amp;"
                                                                       "   find plugins -name src -type d")) 0 -1)
                                                             "\n+")))))
  </code></pre>
  
  <p>When I open a file I get an error: <code>Error while checking syntax automatically: (split-string (substring ...) "\n+") of flycheck-clang-include-path for option "-I" is not a list of strings</code>.</p>