Error: The `add-path` command is disabled.

First of all, thanks for writing this Action!

Currently v1.1 fails with the following error:
```
Error: Unable to process command '::add-path::ninja_bin' successfully.
Error: The `add-path` command is disabled. Please upgrade to using Environment Files or opt into unsecure command execution by setting the `ACTIONS_ALLOW_UNSECURE_COMMANDS` environment variable to `true`. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/
```
This is because the `add-path` command is depreciated by GitHub:

- [GitHub Actions: Deprecating set-env and add-path commands](https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/)

Start by locating the TypeScript GitHub Action code that emits the `::add-path::ninja_bin` command and read how the action updates the runner environment. Use the linked GitHub Actions deprecation notice as the guidance for the replacement, then run the available action checks to confirm v1.1 no longer reports the disabled-command error.

Written by the indexing model from the issue text.