presets: Add ability to specify equivalent to command line --graphviz
As of 3.20.0 you can't set the equivalent of a “–graphviz=graphviz.dot” command line option in a CMakePresets.json preset.
This a request for that feature. This will allow people to avoid having some things set in a preset and other things set on the command line.
See https://discourse.cmake.org/t/cmakepresets-json-and-graphviz/3256