add --relocatable flag to virtualenv in caratekit

[o-smirnov]

Here: https://github.com/caracal-pipeline/caracal/blob/master/caratekit.sh#L2413

@bennahugo tells me this is a proper fix to the Stupidest #! Problem of All Time.

[gigjozsa]

Sorry, this is slightly to cryptic even for me. What is the #! problem and why should we add the --relocatable flag if it is not supported any more? Or is it?

[bennahugo]

Referring to https://stackoverflow.com/questions/10813538/shebang-line-limit-in-bash-and-linux-kernel

As I later mentioned to @o-smirnov it is deprecated. This used to solve this problem.

However, the answer is to go back to virtualenv-less installs and using manual python paths and paths. Installation into custom prefixes can be achieved via:

pip install --install-option="--prefix=$PREFIX_PATH" package_name