[Bug]: Hunter binary cache doesn't account rustc --version

[igor-egorov]

Bug Summary

Two or more packages build with rustc of different versions may get cached for the same hunter toolchain id which will break kagome linkage

Bug Description

Hunter (binary cache) does not account rustc --version while toolchain id or package hash gets calculated.
That may lead to having packages built with different compiler versions, as the result the appearance of rust-std symbols of different versions will break kagome from successful linking.

Possible workaround - combine all the rust packages into single.

Possible solution - expose rustc version to hunter package hash calculator + enforce same version condition.

[igor-egorov]

cc FYI @Harrm @xDimon