How to suppress "WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:"

How do I suppress the below message that shows up in RStudio 1.2.1335 (or later) when installing an R package using install.packages("packagename")? My users do not have or need Rtools, we only have Windows binaries in our custom repo so there is nothing to build. I would very much prefer not to distribute Rtools because it is not necessary, all packages are already built. Thanks!

WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:

https://cran.rstudio.com/bin/windows/Rtools/