no-longer-needed build-dep on execstack

[Steve Langasek]

The nvidia packages in Ubuntu have a build-dep on execstack, as requested in bug #409456.

That bug was filed 13 years ago, about the fact that the upstream binaries were built with executable stack. They've been rebuilt a few times since then, and there are no longer any upstream binaries with an executable stack:

$ find NVIDIA-Linux/ -name *.so* | xargs -n1 readelf -lW | grep GNU_STACK.*E
$ readelf -lW NVIDIA-Linux/nvidia-{smi,xconfig,persistenced} | grep GNU_STACK.*E
$

So the current use of execstack is a no-op.

The execstack binary is built from prelink, which was dropped from Debian over a year ago.

Please drop this build-dependency from all the nvidia packages so that we can drop prelink from the archive.

[Steve Langasek (vorlon)]

NB the readelf commands used above come from https://wiki.ubuntu.com/SecurityTeam/Roadmap/ExecutableStacks