Error building kifmm as a dependency of Bempp

[mscroggs]

Getting error: failed to run custom build command for 'kifmm v1.0.1' (see https://github.com/bempp/bempp-rs/actions/runs/10417668065/job/28852358041)

[skailasa]

Failing at this line in build script

    let workspace_root = find_workspace_root(&crate_dir).expect("Unable to find workspace root");

Should update find_workspace_root to be relative to kifmm