This is somewhat magical issue I really don't know where to ask about. I'm building LLVM in various Linux distros and comparing what I'm getting, all including generated .html files. One of the stunning difference, is the lack of the graphviz images for the ClangRepl.html file. And the diff of this file shows the lines like this missing in the generated ClangRepl.html

<div class="graphviz"><img src="_images/graphviz-7b3ae88c785ecc90fa69fae162f157c2ba60ffaf.png" alt="Shows how Automatic PrintF can be used" class="graphviz" /></div> 

Note that the graphviz package is installed in all of those distros, including SLES.