libpari-gmp is a dependency of many packages, so it's important to be able to use the one from the system.

We check that system's PARI/GP environment is close enough to what we would install in Sage (i.e. versions of GP and libpari, and that they share the datadir). Also, PARI packages need to be checked.

CC: @embray @kiwifb @isuruf @timokau @antonio-rojas

Component: build: configure

Author: Dima Pasechnik

Branch: dd2b3fa

Reviewer: Isuru Fernando

Issue created by migration from https://trac.sagemath.org/ticket/28242