Fix nxflat build error on Ubuntu

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3404 42af7a65-404d-4744-a932-0658087f49c3

Documentation/NuttX.html

@@ -2250,6 +2250,7 @@ buildroot-1.10 2011-xx-xx <spudmonkey@racsa.co.cr>
       under Cygwin.
     * Makefile - Alter copy arguements to avoid permissions problems when
       copying NuttX header files.
+    * toolchain/nxflat/nxflat.mk and Makefile - Fix include paths.
 </pre></ul>
 
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