build: add flag_alias definition for Starlarkification of python flags

[aranguyen]

With this change, when user build with a native python flag, flag_alias will point to the starlark version of the flag. Please see design doc here for more details.

[gemini-code-assist[bot]]

Summary of Changes

Hello @aranguyen, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request integrates flag_alias definitions into the MODULE.bazel file, a critical step in migrating Python build flags to a Starlark-based configuration system. By mapping existing native flags to their new Starlark implementations, the change ensures a smooth transition and consistent behavior for users while advancing the overall Starlarkification initiative.

Highlights

• Starlarkification of Python Flags: This pull request adds flag_alias definitions to MODULE.bazel to facilitate the Starlarkification of Python-related build flags.
• Flag Aliases Added: Specific aliases have been introduced for build_python_zip, incompatible_default_to_explicit_init_py, python_path, and experimental_python_import_all_repositories.
• Mapping to Starlark Versions: These aliases ensure that when native Python flags are used, they correctly point to their Starlark-defined counterparts located under //python/config_settings.

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[rickeylev]

Is flag_alias bazel 9+? All the CI jobs are failing because it's not available.

At the least, we need to support 8.x.

We can drop 7.x pretty soon -- I'm thinking the Jan release?

[gregestren]

This should work as a no-op in the latest bazel 8.x and 7.x releases.

i.e. they continue to read native flags as usual, so they parse these new entries but just skip over them.

[gregestren]

See https://github.com/bazelbuild/bazel/issues/27337 and https://github.com/bazelbuild/bazel/issues/27334.

[rickeylev]

flag_alias() should work with latest 7.x and 8.x releases

Oh ok, that explains. Thanks. I updated the PR and it's using 8.5, but it still fails, error:

ERROR: /workdir/MODULE.bazel:460:11: Traceback (most recent call last):
	File "/workdir/MODULE.bazel", line 460, column 11, in <toplevel>
		flag_alias("build_python_zip", "//python/config_settings:build_python_zip")
Error in flag_alias: flag_alias() got unexpected positional argument

[gregestren]

@aranguyen I think you want to give the parameters names to fix that.

[aignas]

Please also add a changelog note stating the minimum supported bazel versions coming with this change.