[CMake] Warning on --help-command-* when outputting to html

[Mike Jackson]

I get the following warning when trying to save the contents of a  
help command to an html file:

517:[mjackson at thor:bin]$ ./cmake --help-command write_file out.html
WARNING: ComputeSectionLinkPrefix failed for ""


Not sure if this is benign or what, but it does get annoying...

-- 
Mike Jackson   Senior Research Engineer
Innovative Management & Technology Services