Bump target-lexicon to 0.12.6

[msrd0]

Checklist

• I have read the Contributor Guide
• I have read and agree to the Code of Conduct
• I have added a description of my changes and why I'd like them included in the section below

Description of Changes

This crate fails to compile using the current minimum required version of target-lexicon as it does not include the Aix variant used within this crate.

[Jake-Shadle]

This PR doesn't actually change anything, 0.12.6 is semver compatible with the current version string, and is not even the latest version. Try cargo update -p target-lexicon

[msrd0]

Your package does not compile with the minimum version declared in your Cargo.toml. That's a bug.

[msrd0]

@Jake-Shadle My previous comment was maybe a little bit short, let me expand. In Cargo.toml, specifying version X.Y.Z means that any version that is either X.Y.Z or semver-compatible should work for your project. In your case, you are specifying version 0.12.5, meaning that it should compile with 0.12.Z for any Z >= 5.

However, your project does not compile with version 0.12.5. It uses an enum variant introduced in version 0.12.6 of the dependency, therefore 0.12.6 is the minimal version and the one you should specify. I would agree that going from 0.12.6 to 0.12.7 would not actually change anything. But specifying 0.12.5 is what I consider a bug, as it fails to compile with that exact version. (Btw this has happened to me before as well: gotham-rs/gotham#437 (review))

Regarding why I found this problem to begin with: I have several projects that don't include a Cargo.lock file in the git repository as is/was the recommendation for libraries. But every now and then, the CI run that uses the minimum Rust version for my library fails since some dependencies latest semver compatible version requires a newer Rust version. Therefore I tried to generate a minimum version file with cargo -Z minimal-versions update but that meant that some dependencies, including this project, failed to compile, and I had to manually find the actual minimal versions.