Fix compiler warning on Apple/M1/Clang (backport #1857)

[mergify]

This is an automatic backport of pull request #1857 done by Mergify.
Cherry-pick of e667346 has failed:

On branch mergify/bp/0.27-maintenance/pr-1857
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	both modified:   cmake/compilerFlags.cmake

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To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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