Feature: Cross-compile support for aarch64

[omeh-a]

Currently, ipbench does not build easily for anything except x86. It is possible to deploy it to arm via a .deb however, which suggests that this requires minor changes.

This is extremely suboptimal considering the tester machines will almost always be small ARM SBCs, and at TS we often want to benchmark ARM targets.

Goal: Update autotools build process to be able to target AArch64 with a ./configure flag.

Bonus: We can add ipbench to BuildRoot as a package because we often end up using it there. This may make deployment of testers + targets much MUCH MUCH easier.

[omeh-a]

Addendum: does not actually work via .deb.

I managed to get ipbench to compile on an arm machine for arm, although it required tampering with config files.

[omeh-a]

Compiled files on arm do not work. It appears that ipbench is simply impossible to build for arm64 currently. Per the issues in #8, most of the build system is woefully outdated and unfortunately I think the work to actually fix this will be non-trivial and require a lot of understanding of autotools. @wom-bat have you got any thoughts on where to start?

[omeh-a]

Update: this is going to be nearly impossible without a total rewrite of the entire build system - python libraries are particularly challenging. For now, just fixing build on aarch64 will suffice