Looks like some misunderstandings.
By saying "tweaks to build commands", I mean we did some changes to the cmake.xxx config files, so we'll build with libgmp (the steps are listed somewhere below this comment).
Then we remove the libgmp provided bylibgmp-dev package, and build & install our own libgmp from MPIR source. So it will be picked up automatically when building the final binaries.
Any further questions please let me know.