fix build failures

[d-morrison]

https://github.com/d-morrison/qwt/actions/runs/25777035087/job/75711738505

[github-actions]

The GitHub issue titled "fix build failures" highlights a problem with the build process of the repository, as evidenced by a failing workflow run linked in the body (https://github.com/d-morrison/qwt/actions/runs/25777035087/job/75711738505). The issue likely serves as a call to investigate and resolve the errors causing the build failure, ensuring the codebase or CI/CD setup is brought back to a stable and functional state. Additional context or logs may be needed to diagnose the specific cause of the failure.