A script essentially runs `v2-install cabal-install:exe:cabal`,
but does some simple setup, so the result is less luckily
to be influences by environment.

Also improve bootstrap to do out-of-tree builds.

upload v2

split-sections don't do anything on macOS, and make GHC fail, and also don't apply to all packages when specifid this way

Use http, https tricky in some environments