Don't always run php for DPP_CORO

[supsm]

If DPP_CORO is configured to be true, the make_struct.php will always be run, even if not on UNIX or if PHP isn't found. This PR moves the relevant execute_process to where the other php files are run.

(and no, I'm not able to retarget or reopen the other PR)

Code change checklist

• I have ensured that all methods and functions are fully documented using doxygen style comments.
• My code follows the coding style guide.
• I tested that my change works before raising the PR.
• I have ensured that I did not break any existing API calls.
• I have not built my pull request using AI, a static analysis tool or similar without any human oversight.

[netlify]

✅ Deploy Preview for dpp-dev ready!

Name	Link
🔨 Latest commit	d11ec12
🔍 Latest deploy log	https://app.netlify.com/sites/dpp-dev/deploys/678df238a5f94e0008030d3f
😎 Deploy Preview	https://deploy-preview-1363--dpp-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[braindigitalis]

thanks for the contribution :)