CP solver test fails when using nix flake based development environment

[br4sco]

When using the development environment defined in misc/packaging/flake.nix, one of the tests in stdlib/cp/solve.mc fails with

 ** Unit test FAILED: </tmp/miking/stdlib/cp/solve.mc 330:0-337:77> **
    LHS: ['\n','v','a','r',' ','i','n','t',':',' ','x',';','\n','s','o','l','v','e',' ','m','a','x','i','m','i','z','e',' ','x',';','\n']
    RHS: {status = COPSolve_COPUnbounded {}, solutions = []}
    Using: eqTest
  { vCOPSolve_solverOptionsDefault
      {}
    with
    solver =
      "coinbc" }
  false
  [ "x" ] 

After discussing with @lingmar this test should pass with COIN-BC 2.10/1.17 which currently has the same version in the nix unstable channel.