cad/ngspice_rework: Enable X support by default (introduce X11 option)

Ngspice built inside a package builder will not have x11 support which
results in errors such as "Can't open viewport in graphics." when
trying to plot.

This change adds the X11 option which is on by default.

PR: 212357
Submitted by: Michael Neumann
Approved by: Kevin Zheng (maintainer)