Summary:
* Added Docker build environment for RocksJava on s390x
* Cache alignment size for s390x was incorrectly calculated on gcc 6.4.0
* Tighter control over which installed version of Java is used is required - build now correctly adheres to `JAVA_HOME` if it is set
* Alpine build scripts should be used on Alpine (previously CentOS script worked by falling through to minimal gcc version)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9321
Reviewed By: mrambacher
Differential Revision: D33259624
Pulled By: jay-zhuang
fbshipit-source-id: d791a5150581344925c3c3f9cbb9a3622d63b3b6
65996dd757