ci: fix vcpkg cache keys to use target for platforms with multiple targets, allow restore oldkey

.github/workflows/build.yaml

@@ -45,9 +45,10 @@ jobs:
         uses: actions/cache@v4
         with:
           path: target/vcpkg
-          key: ${{ runner.os }}-vcpkg-${{ hashFiles('Cargo.toml', 'Cargo.lock') }}
+          key: vcpkg-${{ runner.os }}-${{ matrix.target }}-${{ hashFiles('Cargo.toml', 'Cargo.lock') }}
           restore-keys: |
-            ${{ runner.os }}-vcpkg-
+            ${{ runner.os }}-vcpkg
+            vcpkg-${{ runner.os }}-${{ matrix.target }}-
 
       - name: Vcpkg Linux Dependencies
         if: runner.os == 'Linux'