Downloads Rtools in app_dir. If it has already been downloaded, get_Rtools will use that file. If the download fails it will stop.
get_Rtools(app_dir, Rtools_version, R_version)Development app's directory, defaults to getwd().
Rtools version to include. For more information, see Building R for Windows.
R version to use. Supports inequalities. Defaults to: paste0(">=", R.version$major, '.', R.version$minor).
sprintf('Rtools%s.exe', gsub("\.", "", Rtools_version)) in app_dir.
If create_app(include_Rtools = TRUE), then get_Rtools.
get_R, copy_installation, create_config, create_bat, directives_section, setup_section, languages_section, tasks_section, files_section, icons_section, run_section, and code_section.