- Set `ENABLE_BAZELISK_MIGRATE` to `1` to enable this feature for BCR
presubmit
- Once enabled, the BCR presubmit will try to fetch incompatible flags
from the `incompatible_flags.yml` file in the BCR root or
`presubmit.yml` of the module.
- Then the script set up env vars to enable bazelisk's
[--migrate](https://github.com/bazelbuild/bazelisk?tab=readme-ov-file#--migrate)
feature to test those incompatible flags. A Bazelisk improvement is
needed at bazelbuild/bazelisk#678.
- The incompatible flag tests can be skipped by applying
`skip-incompatible-flags-test` flag to the BCR PR, which can be
triggered by anyone with comment `@bazel-io skip_check
incompatible_flags`.

In the `incompatible_flags.yml` or `presubmit.yml` file, incompatible
flags can be specified in the following format:
```
incompatible_flags:
  "--incompatible_config_setting_private_default_visibility":
    - 6.x
    - 7.x
    - 8.x
  "--incompatible_disable_native_repo_rules":
    - 7.x
    - 8.x
  "--incompatible_autoload_externally=":
    - 7.x
    - 8.x
  "--incompatible_disable_autoloads_in_main_repo":
    - last_green
    - rolling
```