feat: add spm cache

Author: okwasniewski

.github/workflows/ci.yml

@@ -48,4 +48,4 @@ jobs:
           xcode-version: 15
 
       - name: Test
-        run: xcodebuild -scheme MiniSim -destination 'platform=macOS' -skipPackagePluginValidation -skipMacroValidation test COMPILER_INDEX_STORE_ENABLE=NO
+        run: xcodebuild -scheme MiniSim -skipPackagePluginValidation -skipMacroValidation test COMPILER_INDEX_STORE_ENABLE=NO