CI: give Windows a persistent Cargo target and enable sccache

.github/workflows/ci.yml

@@ -108,6 +108,8 @@ jobs:
         run: |
           if [[ "${RUNNER_OS}" == "Linux" ]]; then
             cargo_target_dir="${HOME}/actions-runner/_work/target"
+          elif [[ "${RUNNER_OS}" == "Windows" && -d "C:/actions-runner/_work" ]]; then
+            cargo_target_dir="C:/actions-runner/_work/target"
           else
             # Forward slashes keep the Windows path compatible with Cargo,
             # PowerShell, GitHub Actions, and Git Bash filesystem commands.
@@ -117,15 +119,21 @@ jobs:
 
       - &configure-sccache
         name: Configure sccache
-        if: runner.os == 'Linux'
         shell: bash
         run: |
           if command -v sccache >/dev/null 2>&1; then
+            if [[ "${RUNNER_OS}" == "Windows" ]]; then
+              sccache_bin="C:/sccache/sccache.exe"
+              sccache_dir="C:/actions-runner/_work/sccache"
+            else
+              sccache_bin="$(command -v sccache)"
+              sccache_dir="${HOME}/.cache/sccache"
+            fi
             # sccache cannot cache incremental compilation artifacts, so
             # disable Cargo's incremental mode whenever the wrapper is active.
             echo "CARGO_INCREMENTAL=0" >>"${GITHUB_ENV}"
-            echo "RUSTC_WRAPPER=/usr/local/bin/sccache" >>"${GITHUB_ENV}"
-            echo "SCCACHE_DIR=${HOME}/.cache/sccache" >>"${GITHUB_ENV}"
+            echo "RUSTC_WRAPPER=${sccache_bin}" >>"${GITHUB_ENV}"
+            echo "SCCACHE_DIR=${sccache_dir}" >>"${GITHUB_ENV}"
             echo "SCCACHE_CACHE_SIZE=20G" >>"${GITHUB_ENV}"
           fi
 
@@ -243,13 +251,13 @@ jobs:
 
       - &show-sccache-stats
         name: Show sccache statistics
-        if: always() && runner.os == 'Linux'
+        if: always()
         shell: bash
         run: |
           if command -v sccache >/dev/null 2>&1; then
             sccache --show-stats
           else
-            echo "::notice::sccache is not installed on this Linux runner"
+            echo "::notice::sccache is not installed on this ${RUNNER_OS} runner"
           fi
 
       - name: Upload Cargo timing reports