arrow

GH-35116: [CI][C++] Enable compile-time AVX2 on some CI platforms (#36662)

AVX2 became mainline on Intel and AMD server CPUs around 2015, so it's unlikely to be unavailable on current cloud platforms:
https://en.wikipedia.org/wiki/Advanced_Vector_Extensions#CPUs_with_AVX2

Enable it at least on one Windows and one Linux CI platform.

x86 macOS is a legacy platform, so less interesting to exercise there (and I'm not sure the old CPUs in x86 Macs actually support AVX2).

Also, fix the buggy AVX2 activation logic in Acero and avoid force-testing AVX2 on incompatible systems.

* Closes: #35116

Authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>