[llvm] [CI] Add link to issue tracker upon job failures (PR #140817)

[David Spickett via llvm-commits]

DavidSpickett wrote:

We don't need to fix this because Buildkite will be going away soon but FYI just in case anyone else reports it...

Buildkite does not render a blank line if this new text is placed directly after the `</details>` tag. Neither does Visual Studio Code's renderer, but Github does. Or maybe they all do but to varying heights, but on Buildkite it's hard to read as a result.

Buildkite:
![Screenshot from 2025-05-29 17-27-52](https://github.com/user-attachments/assets/9ff974fc-4033-42e4-9be7-7210f7a81c17)
Github:
![Screenshot from 2025-05-29 17-29-33](https://github.com/user-attachments/assets/e8df1421-7876-4dd0-b3cc-15e47ad39618)

Also I notice the emoji not working, looks like GitHub doesn't have these I'll try to confirm. If so, :penguin: and :window: could work :)

https://github.com/llvm/llvm-project/pull/140817