[R-SIG-Mac] cmake on build servers

[Jeroen Ooms]

Would it be possible to install cmake on the CRAN macos servers (or if
it is there, add it to the PATH)? Right now it only is available on
the "sonoma" target (arm64 release), see e.g.
https://cran.r-project.org/web/checks/check_results_RcppParallel.html

We could add cmake to the 'recipes' but an easier route is just to
install it from https://cmake.org/download/ (as done for the sonoma
server).

Thank you!

Jeroen