use system compiler for xenial

Author: lordofhyphens

.travis.yml

@@ -19,7 +19,7 @@ before_install:
 
 script:
     - if [[ "${TRAVIS_OS_NAME}" == "linux" && "$TARGET" == "main" ]]; then ./package/linux/travis-build-main.sh -p -b -w || travis_terminate 1; fi
-    - if [[ "${TRAVIS_OS_NAME}" == "linux" && "$TARGET" == "cpp"  ]]; then ./package/linux/travis-build-cpp.sh || travis_terminate 1; fi
+    - if [[ "${TRAVIS_OS_NAME}" == "linux" && "$TARGET" == "cpp"  ]]; then ./package/linux/travis-build-cpp.sh -b -w || travis_terminate 1; fi
     - if [[ "${TRAVIS_OS_NAME}" == "osx"   && "$TARGET" == "main" ]]; then ./package/osx/travis-build-main.sh || travis_terminate 1; fi
     - if [[ "${TRAVIS_OS_NAME}" == "osx"   && "$TARGET" == "cpp"  ]]; then ./package/osx/travis-build-cpp.sh || travis_terminate 1; fi