Added cache for Swift Package Manager in build workflow

Author: tobihagemann

.github/workflows/build.yml

@@ -9,6 +9,12 @@ jobs:
     runs-on: macos-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/cache@v2
+        with:
+          path: .build
+          key: ${{ runner.os }}-spm-${{ hashFiles('**/Package.resolved') }}
+          restore-keys: |
+            ${{ runner.os }}-spm-
       - name: Build and test
         run: set -o pipefail && env NSUnbufferedIO=YES xcodebuild -scheme 'CryptomatorCryptoLib' -destination 'platform=macOS' -enableCodeCoverage YES clean test | xcpretty
       - name: Upload code coverage report