http_file: add root BUILD to improve error when referencing repo root

[abishekgiri]

Summary

• add a repo-root BUILD alias for http_file repositories so @repo//:file resolves from the repository root
• keep the existing file/BUILD target layout while exposing a friendlier root target
• fix the regression test so it is defined before run_suite, uses setup_module_dot_bazel, and validates the correct file checksum

Testing

• bazel test //src/test/shell/bazel:starlark_repository_test --test_filter=test_http_file_root_build_alias --test_output=errors

[meteorcloudy]

Maybe we should have an alias at @repo//:repo so that @repo just works?

[abishekgiri]

Maybe we should have an alias at @repo//:repo so that @repo just works?

Implemented this in 385ff83. http_file now exposes a root alias for the repo name as well, so @repo//:repo and bare @repo resolve to the downloaded file. I also updated the regression coverage accordingly.

[meteorcloudy]

Sorry for the delay here, can you please rebase and run bazel run //src/test/tools/bzlmod:update_default_lock_file to fix the lockfile?

[abishekgiri]

Sorry for the delay here, can you please rebase and run bazel run //src/test/tools/bzlmod:update_default_lock_file to fix the lockfile?

Rebased onto the latest upstream/master and pushed the updated branch. I also refreshed src/test/tools/bzlmod/MODULE.bazel.lock in 0f074080f5.

The helper target bazel run //src/test/tools/bzlmod:update_default_lock_file is still blocked on this machine by the local Xcode license issue during build (xcrun code 69), so I regenerated the lockfile via the same empty-workspace mod deps flow using the checkout’s pinned Bazel version (9.0.1).