add flexible system prerequisites in buildspec

[hboutemy]

PLC4X rebuild requires Git to be available: rebuild.sh can't provide such project-specific requirement yet, it has to be rebuilt by hand without the Docker container

Sometimes, prerequisites may be hard to automatically provide, but it would be useful to have an initial mechanism for simple cases like this one

[hboutemy]

just tested arthas 3.5.1: it requires g++ (was not required for 3.5.0). Perhaps there is a profile or system property to disable this part of the build, that could be a workaround...

[hboutemy]

helix 1.0.3 requires bzip2

[hboutemy]

cucumber html-formatter requires to run npm before doing Maven build

[hboutemy]

many new optional features have been added in #106 and even many common packages like bzip2 https://github.com/jvm-repo-rebuild/reproducible-central/blob/master/bin/docker/Dockerfile.toolchains.template#L48
need to check if it is sufficient or if additional refinements can be useful

[hboutemy]

alluxio requires go