vendoring: Mention rust-cargo-vendor-filterer

[slyon]

The rust-cargo-vendor-filterer package is newly available as of Plucky (and soon to be in Debian), thanks to @julian-klode .

The MIR Rust vendoring docs can probably make some good use of it.

[julian-klode]

There's a bunch of irregularieties with rust-vendor/ vs debian/rust-vendor in the commit and in the page already.

We need to sort out armhf too, it unfortunately does not end in gnu, for sqv I currently have:

env -i cargo-vendor-filterer -F crypto-openssl --no-default-features --tier 2 --platform '*-*-linux-gnu' --platform '*-*-linux-gnueabi' $(CARGO_VENDOR_DIR)

[slyon]

Moving to "Draft", as Julian might want to improve upon this.

[didrocks]

For reference, this is what we did in authd:

• running when building the source package: https://github.com/ubuntu/authd/blob/main/debian/vendor-rust.sh
• our config (difference with here was to use "tier2": https://github.com/ubuntu/authd/blob/main/Cargo.toml#L9)

[julian-klode]

@didrocks Ah you're missing armhf there as a platform which is *-unknown-linux-gnueabihf

[didrocks]

@julian-klode good point! Will amend this.