misc: Add script to fetch build artifacts and impersonate jenkins environment

This is useful to fetch and quickly set up an approximation of the
environment that a jenkins build is run in for the LTTng CI.

Ex:

```
./scripts/jenkins_job_env.py fetch \
  -j lttng-tools_master_linuxbuild \
  -jc
  babeltrace_version=stable-2.0,build=std,conf=agents,liburcu_version=master,platform=deb12-amd64 \
  -b 157 \
  destination_dir
```

The script will download and unpack the archives, rebuilding symlinks
for the shared objects in `archive/deps/build/{lib_dir_arch}`, and
create two scripts to activate and deactivate the typical environment
variables in `destination_dir/{activate,deactivate}`.

Change-Id: I2bfcb213dfc0c066b91c5f70a596c1ec5e5019ff
Signed-off-by: Kienan Stewart <kstewart@efficios.com>