Travis: remove Mroonga for clang

Mroonga generated far too many warnings (and hence output) for Travis's
sensibilities on output log file size. So we just remove the storage
engine.
Signed-off-by: Daniel Black <daniel.black@au.ibm.com>

.travis.yml

@@ -72,6 +72,10 @@ addons:
 # libsystemd-daemon-dev # https://github.com/travis-ci/apt-package-whitelist/issues/3882
 
 script:
+# mroonga just generates too many warnings with clang and travis stops the job
+  - if [[ "${TRAVIS_OS_NAME}" == 'linux' && "${CXX}" == 'clang++' ]]; then
+      rm -rf "${TRAVIS_BUILD_DIR}"/storage/mroonga;
+    fi   
   - source .travis.compiler.sh
   - ${MYSQL_BUILD_CC} --version ; ${MYSQL_BUILD_CXX} --version
   - cd "${TRAVIS_BUILD_DIR}"