Upload CRAN scripts for Linux

[statnmap]

Why ?

• Received link to CRAN check scripts
• Need an exploration and tests on different flavours

What?

• Scripts and env. variables for package incoming checks by Kurt
• Scripts and env. variables for CRAN regular checks of all packages

issue

issue #17

[llrs]

Given that the scripts are already mirrored in github: https://github.com/r-devel/r-dev-web I think it would make sense to close the PR unless they add something like (https://github.com/RConsortium/r-repositories-wg/pull/18/commits/cf9e040275fcace714e1f3b7ea394c7eabface2f). But I'm not sure how to keep those changes in sync with the updates the CRAN team does with source and keep them runnable.