Imporved the dependecy detection for runtime on macosx

Summary: Changed FindMumps to run a small code that solves a 2x2 system to try to detect libraries that are missing at runtime for mumps on MacOS

Test Plan: Test it also on Linux

Reviewers: #akantu-developers, anciaux, jasper, volmer, nrichart, kammer

Reviewed By: #akantu-developers, anciaux

Subscribers: anciaux

Tags: Akantu

Differential Revision: https://c4science.ch/D122