feat: implement tars symlinks

[thesayyn]

fixes #508, needs #558 first.

[thesayyn]

@gregmagolan is case you are interested, this is the one that will make RBE go fast.

[mortenmj]

Seeing a lot of very similar errors when testing this one. At the surface, it looks like this broke all of our images that we pass tars to (built with pkg_tar in our case). It looks like it's only a problem with remote execution. This is using Bazel 7.1.1.

Example output:

$ bazel build //services/tracing/lightstep-otel-collector:image_with_config_for_validation
INFO: Invocation ID: 66e79d22-3878-4a31-8524-b7c8ea9b4cca
INFO: Analyzed target //services/tracing/lightstep-otel-collector:image_with_config_for_validation (0 packages loaded, 0 targets configured).
ERROR: /workspaces/infrastructure/services/tracing/lightstep-otel-collector/BUILD.bazel:28:6: TreeArtifact services/tracing/lightstep-otel-collector/image_with_config_for_validation.image was not created
ERROR: /workspaces/infrastructure/services/tracing/lightstep-otel-collector/BUILD.bazel:28:6: OCI Image //services/tracing/lightstep-otel-collector:image_with_config_for_validation.image failed: not all outputs were created or valid
Target //services/tracing/lightstep-otel-collector:image_with_config_for_validation failed to build
INFO: Elapsed time: 0.782s, Critical Path: 0.03s
INFO: 2 processes: 1 remote cache hit, 1 internal.
ERROR: Build did NOT complete successfully

[thesayyn]

That is interesting, do you have more information on this? eg which service are you using?

[thesayyn]

This could be a Bazel bug!

[alexeagle]

Long journey to get here!

[mortenmj]

That is interesting, do you have more information on this? eg which service are you using?

We use Buildbarn. As far as I can tell, from looking at what got scheduled remotely, this never hit the build cluster at all.

Happy to help debug it.