Cache test deps on Windows

.github/workflows/ci.yml

@@ -223,6 +223,7 @@ jobs:
           extra_test_args: --workspace --exclude tokio-boring --exclude hyper-boring
     env:
       CARGO_HOME: ${{ github.workspace }}/.cache/cargo
+      CARGO_BUILD_BUILD_DIR: ${{ github.workspace }}/.cache/build-dir
     steps:
     - uses: actions/checkout@v4
       with:
@@ -293,6 +294,17 @@ jobs:
     - name: Set Android Linker path
       if: endsWith(matrix.thing, '-android')
       run: echo "CARGO_TARGET_$(echo ${{ matrix.target }} | tr \\-a-z _A-Z)_LINKER=$ANDROID_NDK/toolchains/llvm/prebuilt/linux-x86_64/bin/$(echo ${{ matrix.target }} | sed s/armv7/armv7a/)21-clang++" >> "$GITHUB_ENV"
+    - name: Fetch deps
+      run: cargo fetch --target ${{ matrix.target }}
+      shell: bash
+      env: ${{ matrix.custom_env }}
+      # Windows builds are the slowest
+    - name: Cache deps in Windows tests
+      if: startsWith(matrix.os, 'windows')
+      uses: actions/cache@v4
+      with:
+        path: .cache/build-dir # CARGO_BUILD_BUILD_DIR
+        key: test-${{ matrix.target }}-${{ hashFiles('Cargo.lock') }}
     - name: Build tests
       # We `build` because we want the linker to verify we are cross-compiling correctly for check-only targets.
       run: cargo build -v --target ${{ matrix.target }} --tests ${{ matrix.extra_test_args }}