relates to #301

this should at first try to pass external ./target dir to the right place into container, and then, if that can be made to work, ~/.cargo folder too

    /Users/runner/.cargo/bin
    /Users/runner/.cargo/.crates2.json
    /Users/runner/.cargo/.crates.toml
    /Users/runner/.cargo/git
    /Users/runner/.cargo/registry/cache
    /Users/runner/.cargo/registry/index
    ./target

NOTE: original discussion of docker volumes somewhere in tg only mentioned rebuilding the same crate after initial
build for reduced build times, the task has had an obvious scope extension, where a sequence of builds of crates in the same workspace have to be passed initial cache, and then all built sequentially, while sharing the same cache.
Original description:
1i -> 1C
(C stands for Cache, 1i is non-cached build of crate 1, 1C is cached build of crate 1 with cache obtained during 1i )
Extended description:
sequential build of multiple crates or workspace: EC -> 1EC , EC -> 2EC, EC -> 3EC ...
(EC stands for External Cache, 1EC is cached build of crate 1 with cache supplied externally)