Work around SwiftyLab/setup-swift#315 (#1595)

Author: dabrahams

.github/workflows/build-and-test.yml

@@ -238,6 +238,7 @@ jobs:
         uses: SwiftyLab/setup-swift@latest
         with:
           swift-version: ${{ env.swift-version }}
+          cache-snapshot: false # Workaround for https://github.com/SwiftyLab/setup-swift/issues/315
 
       - uses: compnerd/gha-setup-vsdevenv@main
       - name: Set up swift (Windows)

.github/workflows/doc-extraction.yml

@@ -46,6 +46,7 @@ jobs:
       uses: SwiftyLab/setup-swift@latest
       with:
         swift-version: ${{ env.swift-version }}
+        cache-snapshot: false # Workaround for https://github.com/SwiftyLab/setup-swift/issues/315
 
     - name: Install LLVM
       # 7z doesn't support decompressing from a stream or we'd do this all as one statement. Maybe