Add URL of Z3 issue for checkAssumptions

Author: jad-hamza

src/main/scala/inox/solvers/combinators/NonIncrementalSolver.scala

@@ -52,6 +52,7 @@ trait NonIncrementalSolver extends AbstractSolver { self =>
       currentSolver = Some(newSolver)
       for (expression <- assertions)
         newSolver.assertCnstr(expression)
+      // we assert the assumptions to address: https://github.com/Z3Prover/z3/issues/5257
       for (assumption <- assumptions)
         newSolver.assertCnstr(assumption)
       val res = newSolver.checkAssumptions(config)(Set())