Handle manually the checkout step
Handle manually the checkout step

Currently, `git lfs checkout` is much more efficient to download LFS data
than `git checkout` (50s / 4min).

orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB