[Bioc-devel] vignettes with different builders in one package?

Am I correct that this is not allowed?  I have an old Sweave vignette
and a newer Rmd vignette in gwascat but do not see how to build
so that both vignettes are properly situated in the installed doc folder.
The WRE manual doesn't address multiple builders.  So I am planning
to translate the older one to Rmd.