travis: osx install zstd lz4 snappy xz (#3893)

Summary:
test osx against the brew libraries zstd, lz4, snappy, xz.
Closes https://github.com/facebook/rocksdb/pull/3893

Differential Revision: D8461988

Pulled By: siying

fbshipit-source-id: cc2a8487bcb1e98ca05bddd3a509a6896258ccf8

.travis.yml

@@ -52,7 +52,7 @@ matrix:
 # https://docs.travis-ci.com/user/caching/#ccache-cache
 install:
   - if [ "${TRAVIS_OS_NAME}" == osx ]; then
-      brew install ccache;
+      brew install ccache zstd lz4 snappy xz;
       PATH=$PATH:/usr/local/opt/ccache/libexec;
     fi
   - if [[ "${JOB_NAME}" == cmake* ]] && [ "${TRAVIS_OS_NAME}" == linux ]; then