zed: Read ZED_COMMIT_SHA from env var when building (#51115)

Quality-of-life improvement for us Nix users - Zed built via `nix build`
will now correctly the git commit sha in its version

<img width="433" height="298" alt="image"
src="https://github.com/user-attachments/assets/b940ee4a-6914-4410-ba20-b50391282a4e"
/>

Release Notes:

- N/A
e0b1f8a525Jakub Konka committed on 3/9/2026, 4:02:09 PM· committed by GitHubparent850188f
3 files changedLine totals unavailable