Fix macOS legacy build breakage caused by std::filesystem

[claucambra]

std::filesystem is not supported on macOS under 10.15

[claucambra]

/backport to stable-3.12

[backportbot]

The backport to stable-3.12 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable-3.12
git pull origin stable-3.12

# Create the new backport branch
git checkout -b backport/6583/stable-3.12

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 7c2f4141 5f7d911e

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/6583/stable-3.12

Error: Failed to cherry pick commits: error: no cherry-pick or revert in progress
fatal: cherry-pick failed

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[sonarcloud]

Quality Gate failed

Failed conditions
D Maintainability Rating on New Code (required ≥ A)
31 New Code Smells (required ≤ 0)

See analysis details on SonarCloud

Catch issues before they fail your Quality Gate with our IDE extension SonarLint

[nextcloud-desktop-bot]

AppImage file: nextcloud-PR-6583-5f7d911e324f206902d5fe27ca61ec235f1f6ef4-x86_64.AppImage

To test this change/fix you can simply download above AppImage file and test it.

Please make sure to quit your existing Nextcloud app and backup your data.