### Bug Description Given a part with a `build-environment` (ref. #1217), changing the value of the variables doesn't cause a rebuild of the part. ### To Reproduce ``` $ snapcraft --verbose build --debug serde # change `CARGO_PACKAGES` $ snapcraft --verbose build --debug serde ``` ### part yaml ```shell serde: source: https://github.com/serde-rs/serde source-type: git source-tag: v1.0.215 source-depth: 1 source-subdir: serde plugin: cargo-use build-environment: - CARGO_PACKAGES: serde serde_derive ``` ### Relevant log output ```shell $ snapcraft --verbose build --debug serde # ... Initialising lifecycle Rust is installed on the system, skipping rustup Installing build-packages Skipping pull for serde (already ran) Skipping build for serde (already ran) ```