fix: include Ruby version in CI cache key

Author: seuros

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
             ~/.cargo/registry
             ~/.cargo/git
             tmp
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          key: ${{ runner.os }}-${{ matrix.ruby }}-cargo-${{ hashFiles('**/Cargo.lock') }}
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}