title: Intermittent, random 'file not found' errors under Windows Subsystem for Linux (WSL)
body: <p>I'm getting intermitting 'fatal error: ... file not found' errors building C++ application using either gcc 4.8 or clang 3.8 under Ubuntu 16.04.2 running in Windows Subsystem for Linux (WSL), when including C++ header files, but only since installing the Windows 10 April update (Version 1803, OS Build 17134.1) a few days ago.</p>
  
  <p>Example error message from clang compiler:</p>
  
  <p><code>fatal error: 'boost/preprocessor/list/fold_left.hpp' file not found</code></p>
  
  <p>Example error message from gcc compiler:</p>
  
  <p><code>fatal error: boost/mpl/aux_/at_impl.hpp: No such file or directory</code></p>
  
  <p>I say the error is intermittent because if I re-run the build, the particular error that interrupted the build disappears, and the build runs for a while longer until it either builds successfully or randomly fails to include some other file with the same kind of 'file not found' error.</p>
  
  <p>The timing of this fault and the randomness of it make me suspect it is a new bug in WSL. Anyone else seeing this or have suggestions on how to fix it?</p>
  
  <p>The error is not always in a Boost include, but often is simply because Boost comprises a large proportion of the overall include files. The files being built exist on a shared volume under /mnt/d/.</p>