To build binary packages on windows, Rtools (found at https://cran.r-project.org/bin/windows/Rtools/) needs to be on the path. The default installation process does not add it, so this script finds it (looking first on the path, then in the registry). It also checks that the version of rtools matches the version of R.
setup_rtools(cache = TRUE, debug = FALSE)if TRUE will used cached version of RTools.
if TRUE prints a lot of additional information to
help in debugging.
Either a visible TRUE if rtools is found, or an invisible
FALSE with a diagnostic message.
As a side-effect the internal package variable rtools_path is
updated to the paths to rtools binaries.
This code borrows heavily from RStudio's code for finding rtools. Thanks JJ!