Using cargo clippy without rustup

My Problem

I work on an air-gapped system. Therefore I currently need to install cargo without rustup. However cargo clippy is only available as part of the rustup toolchain (I get error: no override and no default toolchain set if I execute cargo clippy).
cargo-driver works fine, however working on complex projects with many dependency means this is no solution for me.

Potential Solutions

I would like to run cargo clippy on my air-gapped system. I see two possible solutions:

1. Allow rustup to run on offline systems.
2. Allow cargo clippy to run without rustup.

I am unsure how much work an rustup independent clippy would be, or even why this restriction is currently in place. "rustup on offline systems" seems like a very hard problem to tackle.

Notes

I have also opened a ticket in cargo's tracker https://github.com/rust-lang/cargo/issues/9505 but was pointed to this project instead.

Start by tracing how cargo clippy is exposed through rustup and reviewing the Cargo integration; the issue names no source files or tests. Determine whether offline rustup support or rustup-independent invocation is in scope, then verify the selected behavior by running cargo clippy without rustup on an air-gapped system.