Run tests using xcodebuild

I'd rather use swift test, but can't find a way to send coverage report
to coveralls without parsing the profdata myself.

.circleci/config.yml

@@ -5,16 +5,16 @@ jobs:
       xcode: "10.2.0"
     steps:
       - checkout
-      - run: bundle install      
+      - run: bundle install
       - run:
-          name: Run Tests
+          name: Generate xcode project for code coverage
           command: |
-              swift test --enable-code-coverage 2>&1 |
-              xcpretty --report html --output test_output/results.html --report junit --output test_output/unit-tests/results.xml
+              swift package generate-xcodeproj --enable-code-coverage         
       - run:
-          name: Generate xcode project for code coverage
+          name: Run Tests
           command: |
-              swift package generate-xcodeproj
+              xcodebuild -scheme Config-Package test |
+              xcpretty --report html --output test_output/results.html --report junit --output test_output/unit-tests/results.xml
       - run:
           name: Post Coverage
           command: bundle exec slather              

.slather.yml

@@ -2,7 +2,6 @@ coverage_service: coveralls
 ci_service: circleci
 xcodeproj: Config.xcodeproj
 scheme: Config-Package
-build-directory: ./build/debug/codecov
 ignore:
   - .build/*
   - Carthage/*