Build Singularity images in CI
Adds building tasks for Singularity containers for master and staging branches.
Usage docs: https://gitlab.kwant-project.org/qt/cookbook/-/blob/master/hpc05/singularity.md
Adds building tasks for Singularity containers for master and staging branches.
Usage docs: https://gitlab.kwant-project.org/qt/cookbook/-/blob/master/hpc05/singularity.md