Ensure cargo tarpaulin is using same Rust version as Akri

[kate-goldenring]

Describe the bug
Akri's code coverage checks with cargo tarpaulin are currently failing because cargo tarpaulin is using the 1.63 rust toolchain while Akri is using 1.61.

cargo tarpaulin should be inferring Rust version from the Cargo.toml. However, instead of checking each package's Cargo.toml (see the agent's) and installing and using a potentially different toolchain for each, it may just be checking the base Cargo.toml. However, since our base toml represents the larger workspace of projects, it cannot specify a version, so it appears that tarpaulin just uses latest stable in this case.

Investigation should be done as to whether the CARGO_PACKAGE_VERSION env var can be explicitly set to a specific rust version in the workflow when running tarpaulin in a container.

[adithyaj]

I'll take this one, I'll try to see if we can set the env var itself and worst case we can update rust and move forward for now.

[bfjelds]

i wonder if you couldn't do something like this:

docker exec $(cat container_id.txt) sh -c "rustup install 1.61.0"
docker exec $(cat container_id.txt) sh -c "rustup override set 1.61.0"

[bfjelds]

i wonder if you couldn't do something like this:

docker exec $(cat container_id.txt) sh -c "rustup install 1.61.0"
docker exec $(cat container_id.txt) sh -c "rustup override set 1.61.0"

seems to work. i created this PR: #503 ... when i cherry-picked the changes onto #498, the tarpaulin run succeeded: https://github.com/project-akri/akri/runs/8102394108?check_suite_focus=true

[adithyaj]

Thanks Brian!