[skip ci] move to activation json

[wolfv]

The activation scripts were pretty weird and broken.

The "backup" was never useful (we never overwrote the flags anyways).

The sed command didn't work on Windows.

This is an attempt to use the env_vars.d JSON files instead and write the values properly using a little Python helper script.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found some lint.

Here's what I've got...

For recipe/meta.yaml:

• ❌ In conda-forge.yml: $.github_actions = {'resize_win_partitions': True, 'self_hosted': True, 'store_build_artifacts': True, 'timeout_minutes': 1440, 'triggers': ['push', 'pull_request']}.

  {'resize_win_partitions': True, 'self_hosted': True, 'store_build_artifacts': True, 'timeout_minutes': 1440, 'triggers': ['push', 'pull_request']} is not valid under any of the given schemas

  Schema

  {
    "anyOf": [
      {
        "$ref": "#/$defs/GithubActionsConfig"
      },
      {
        "type": "null"
      }
    ]
  }

For recipe/meta.yaml:

• ℹ️ The recipe is not parsable by parser conda-souschef (grayskull). This parser is not currently used by conda-forge, but may be in the future. We are collecting information to see which recipes are compatible with grayskull.
• ℹ️ The recipe is not parsable by parser conda-recipe-manager. The recipe can only be automatically migrated to the new v1 format if it is parseable by conda-recipe-manager.

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/23801066421. Examine the logs at this URL for more detail.}

[hmaarrfk]

don't you want to bump the build number?

[ruben-arts]

What about merging it into #496? Then we can skip having two builds that solve related issues.