Use pkgbuild::with_build_tools() in rcmcheck

[jimhester]

Right now rcmdcheck doesn't ensure the build tools are on the PATH, so you can get failures on Windows even if you have RTools installed unless you explicitly use pkgbuild::with_build_tools(). We could have rcmdcheck instead do this automatically.

Note RStudio does put RTools on the PATH when you run it via the build pane, but not if you run directly in the console.