I guess the user level makevars is just as good, from the admin manual:
> The R system and package-specific compilation flags can be overridden or added to by setting the appropriate Make variables in the personal file HOME/.R/Makevars-R_PLATFORM (but HOME/.R/Makevars.win or HOME/.R/Makevars.win64 on Windows), or if that does not exist, HOME/.R/Makevars,
> Dear all,
> is there a way to set R_MAKEVARS_SITE (or something else), so that R
> finds Makevars.site for multiple archs?
> AFAICT the only option is to put the arch directories in R.home(). But
> I might be missing something.
> My goal is to set different make variables for 32-bit and 64-bit R on
> Windows, without modifying R.home().
> Thank you,