twoliter: disallow std::path::Path::canonicalize

[cbgbt]

Issue number:

Closes #427

Description of changes:
Twoliter uses the location of Twoliter.toml to locate the rest of the Twoliter workspace. Prior to this change, it used std::fs::canonicalize to do so. This function resolves symlinks on the filesystem, which is a problem when you're building in the context of a symlink farm.

This change moves to using path-absolutize for such canoncicalization, which uses unix separator and path traversal semantics to "canonicalize" a path without resolving symlinks or actually consulting with the host's filesystem.

The change also adds clippy lints to attempt to forbid future use of canonicalization functions that can cause this to regress.

See #427 for more details.

Testing done:

• New integration tests pass
• Created a twoliter workspace where Twoliter.toml was a symlink to another workspace. Issuing a build on the old version caused build artifacts to be placed in the build directory behind the symlink. With the new change, build artifacts were placed in the new workspace as expected.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[sumukhballal]

Nice!

[mikn]

You were so quick closing this out I didn't even notice! Thank you @cbgbt ❤️