title: Strange include path in Eclipse CDT + GNU ARM
body: <p>After tinkering with some project settings, namely changing the FPU type, some strange entries appeared in the includes, eg.: </p>
  
  <blockquote>
    <p>project/#undef __ARM_NEON</p>
  </blockquote>
  
  <p>These are not shown at any of the usual places where includes can be specified (C/C++ build -> Settings -> tool settings -> compiler xy -> Includes. </p>
  
  <p>This obviously invalid include path creates an annoying warning message at the "problems" tab.</p>
  
  <p>Sometimes tinkering more with the FPU settings will make these entries disappear, or cause more similar entries to appear, but I could not see any logical behavior here. Is this a bug?</p>
  
  <p><a href="https://i.stack.imgur.com/i4G99.png" rel="nofollow noreferrer">Screenshot</a></p>