Add matrix.os to cache key (ruby#2671)

* Add matrix.os to cache key
* Use multi-line string instead of array
  ref actions/cache#44

Author: znz

Diff for: .github/workflows/windows.yml

@@ -25,17 +25,19 @@ jobs:
       - uses: actions/cache@v1
         with:
           path: C:\vcpkg\downloads
-          key: ${{ runner.os }}-vcpkg-download-${{ github.sha }}
+          key: ${{ runner.os }}-vcpkg-download-${{ matrix.os }}-${{ github.sha }}
           restore-keys: |
+            ${{ runner.os }}-vcpkg-download-${{ matrix.os }}-
             ${{ runner.os }}-vcpkg-download-
       - name: Install libraries with vcpkg
         run: |
           vcpkg --triplet x64-windows install readline zlib
       - uses: actions/cache@v1
         with:
           path: C:\Users\runneradmin\AppData\Local\Temp\chocolatey
-          key: ${{ runner.os }}-chocolatey-${{ github.sha }}
+          key: ${{ runner.os }}-chocolatey-${{ matrix.os }}-${{ github.sha }}
           restore-keys: |
+            ${{ runner.os }}-chocolatey-${{ matrix.os }}-
             ${{ runner.os }}-chocolatey-
       - name: Install libraries with chocolatey
         run: |