#105 Second patch set for improving scripts to do u-boot tarball releases

Hi, This patch set contains various improvements to the scripts to do u-boot tarball releases. In addition it also adds tests for it: since the tarballs should be reproducible it's a good idea to have tests. I also added --help in all the download scripts while I was at it. I'm not sure if that works with pull request but I also tagged the 8833be159bfff1c417a7459dec323384bcbcb4d0 commit (scripts: download: u-boot: fix u-boot repository URL) as u-boot-libre-2021.07-r1. Then the next step will be to actually release the files on the mirrors. Denis.

looks good to me. merging