Travis GoogleUtilities : skip Swift tests when --use-libraries (#6735)

* Travis GoogleUtilities :  skip Swift tests when --use-libraries

* Temporary enable cron tests for PRs to check

* Revert temp change

Author: maksymmalyhin

.travis.yml

@@ -186,9 +186,9 @@ jobs:
         - PROJECT=GoogleUtilitiesCron METHOD=pod-lib-lint
       script:
 
-        - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-libraries --platforms=ios
-        - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-libraries --platforms=tvos
-        - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-libraries --platforms=macos
+        - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-libraries --platforms=ios --skip-tests
+        - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-libraries --platforms=tvos --skip-tests
+        - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-libraries --platforms=macos --skip-tests
         - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-modular-headers --platforms=ios
         - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-modular-headers --platforms=tvos
         - travis_retry ./scripts/pod_lib_lint.rb GoogleUtilities.podspec --use-modular-headers --platforms=macos