in vscode the environment variables without an equals sign are ignored
https://github.com/devcontainers/cli/blob/main/src/spec-node/utils.ts#L488-L498
Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #53470

Release Notes:

- Fix environment variables without an equals sign were treated as fatal
parsing errors.