gh-37011: allowing external ECM to be called gmp-ecm or ecm
ECM executable in Fedora is called `gmp-ecm`
This PR allows both names, `ecm` and `gmp-ecm`, to be used
URL: https://github.com/sagemath/sage/pull/37011
Reported by: Dima Pasechnik
Reviewer(s): Dima Pasechnik, Enrique Manuel Artal Bartolo, Gonzalo Tornaría, Matthias Köppe, Michael Orlitzky, Tobias Diez
