Previously, we were using 8.0.0rc1.
In particular, this upgrade means we need to explicitly
import more rules, as they've been moved out of the core bazel repo.
Our existing configure-baseline scripts would give the wrong result if a `vendor` directory wasn't at the root of the repository, or if the `CODEQL_EXTRACTOR_GO_EXTRACT_VENDOR_DIRS` variable was set to `true` indicating the user wants their vendored code scanned.
Here I replace the shell scripts that implemented the very simplest behaviour with a small Go program.
It turns out everything that is needed for the installer to work on
windows is enabling runfiles. This also requires symlinks to avoid
excessive copying of files.
