Optimize dependencies building of a group of targets

[mudler]

We need to optimize build dependencies which are shared between targets, maybe by also building them before and then start the concurrent builds. we cannot miss --nodeps and --depsonly on the build command while developing this feature.

• build --nodeps A B C
• build --onlydeps A B C
• build --shared A B C (builds the shared deps first, then builds the other concurrently, which probably should be default behavior that can be turned off)
• We should build first those that have no revdep

[geaaru]

I think that it's needed to integrate a logic for load in docker instance the layer/build image found, this permit to reuse previously built images in a new task/env at the same way of the current mode that skips the existing images.
Currently, the skip feature doesn't work if it used with the previously built namespace for only deps (for example) if images aren't available on docker instance of the new env.
WDYT?