boost: Kill unnecessary 'lib' output

This was split in somewhere pre-2014 without the current infra which
automates parts of this, in particular the output propagation.

pkgs/development/libraries/folly/default.nix

@@ -28,7 +28,7 @@ stdenv.mkDerivation rec {
     patchShebangs build
   '';
 
-  configureFlags = [ "--with-boost-libdir=${boost.lib}/lib" ];
+  configureFlags = [ "--with-boost-libdir=${boost.out}/lib" ];
 
   enableParallelBuilding = true;