Add option to use pre-build iceoryx libraries

[elBoberido]

Currently iceoryx is build together with iceoryx-rs. There might be cases where it is desired to use pre-build iceoryx libraries to guarantee binary compatibility with the static libs.

This could be done by an environment variable which can be checked in build.rs. In this case It should also be possible to use dynamic libraries.

This should be done after #7

[elBoberido]

@ZhenshengLee I might borrow some stuff from your build.rs from iceoryx-rs-c :)

[AlexanderEkdahl]

I would suggest separating this into a *-sys crate for better interoperability with non-cargo systems. Detailed documentation of this pattern https://kornel.ski/rust-sys-crate