Provide option to reuse tarball for grid submission

It looks like the grid submission script is currently configured to regenerate a new tarball for every call

https://gitlab.cern.ch/easyjet/easyjet/-/blob/main/EasyjetHub/bin/easyjet-gridsubmit#L154

which means combined submission scripts like https://gitlab.cern.ch/easyjet/easyjet/-/blob/main/bbyyAnalysis/scripts/RunOnGrid_DataMC_Run2.sh#L12

a bit heavy to run.

Some option to reuse the existing tarball might be useful.

It should still be kept disabled by default, as we don't want for old compiled version of the code to be shipped to the grid without the user noticing.