CI: Build using `OCTEZ_RUST_DEPS_TARGET_DIR`

I’m experimenting with setting OCTEZ_RUST_DEPS_TARGET_DIR and caching the resulting dir in the CI. First results seem interesting, although we probably want to explore more.

For regular build of released binaries

• First run: https://gitlab.com/tezos/tezos/-/jobs/8518243729 (27 minutes 4 seconds)
• Second run: https://gitlab.com/tezos/tezos/-/jobs/8518589242 (12 minutes 12 seconds)
• Rebase: https://gitlab.com/tezos/tezos/-/jobs/8521198350 (16 minutes 14 seconds)
• Second rebase: https://gitlab.com/tezos/tezos/-/jobs/8528821410 (15 minutes 30 seconds)
• Merge run !15715 (merged) (without this): https://gitlab.com/tezos/tezos/-/jobs/8528608900 (24 minutes 57 seconds)
• Rebase on top of !15715 (merged): https://gitlab.com/tezos/tezos/-/jobs/8529262724 (20 minutes 18 seconds)

For static build

• First run: https://gitlab.com/tezos/tezos/-/jobs/8518243716 (30 minutes 51 seconds)
• Second run: https://gitlab.com/tezos/tezos/-/jobs/8518633851 (18 minutes 45 seconds)
• Rebase: https://gitlab.com/tezos/tezos/-/jobs/8521198343 (22 minutes 39 seconds)
• Second rebase: https://gitlab.com/tezos/tezos/-/jobs/8528821408 (27 minutes 1 second)
• Merge run !15715 (merged) (without this): https://gitlab.com/tezos/tezos/-/jobs/8528608895 (29 minutes 43 seconds)
• Rebase on top of !15715 (merged): https://gitlab.com/tezos/tezos/-/jobs/8529262720 (35 minutes 53 seconds )
  • Second run: https://gitlab.com/tezos/tezos/-/jobs/8529760515 (20 minutes 10 seconds)

Manually testing the MR

Rebase your MR on top of this one and try to see the impact on build time in the CI?

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR