When building on osx (using macports, gcc4.8, etc) everything builds except DRAW, The native versions of Tcl/Tk use the aqua window system and not X11, I've tried adding #include<X11/Xlib.h> to Draw_Window.cxx but still get the following error
If you are focused on Mac support, I suggest you better try 6.6 beta (already available for downloading), because it provides support of native Cocoa, and contains some more fixes done specially to improve Mac support.
At the same time I would like to note that OCCT v6.5.5 can be built with the latest WOK (Code::Blocks, Xcode should work as well) in the same way as the v6.6.0. But it can be built only with X11 libs, as it does not contain any patches related to Cocoa support. Also v6.5.5 does not include patch 23241, so DRAWEXE will crash on startup.