Fix jni library name for PowerPC Architecture

[ayappanec]

Right now, building rocksdbjava in PowerPC is broken due to JNI library name. I figured it out that "uname -m" and java's os.arch matches in PowerPC architecture. I made use of this advantage to fix the issue. More info can found from this issue --> #1317

[ayappanec]

I also set it up a CI for rocksdb on PowerPC.

http://140.211.168.68:8080/job/Rocksdb/

[ayappanec]

The Travis CI failure is not related to this PR.

[facebook-github-bot]

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[adamretter]

Looks good to me

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@siying has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[bharatviswa504]

@adamretter rocksdb jar from next release will it have ppc so?

[ayappanec]

@bharatviswa504 Good point. We are also waiting for the new release to have ppc library in rocksdb jar.
@adamretter If you have any issues with regarding to Power hardware, i can help you.

[adamretter]

@bharatviswa504 I do not have access to a PPC system on which I could build the binaries. @bharatviswa504 Is that something you could help with?

[ayappanec]

@adamretter I have this jenkins CI running in Ubuntu 16.04.1 ppc64le for rocksdb http://140.211.168.68:8080/job/Rocksdb/.

If you need machine credentials to do your own build, i can share with you.

[adamretter]

@ayappanec That would be perfect. Can you email me the details - adam DoT retter AT googlemail .com

[ayappanec]

@adamretter Just mailed you the details

[bharatviswa504]

@ayappanec Thanks for providing machine.
@adamretter So from next build we will have ppc64le support in rocksdb jar, awesome