Make zstd position independent
Make zstd position independent

Summary: Closes https://github.com/caffe2/caffe2/pull/1975

Differential Revision: D7012872

Pulled By: sf-wind

fbshipit-source-id: 31a8f787faf99894ac25508d85e1eb0f0e8e84a2

Yangqing/caffe2,Yangqing/caffe2,xzturn/caffe2,xzturn/caffe2,Yangqing/caffe2,Yangqing/caffe2,xzturn/caffe2,Yangqing/caffe2,xzturn/caffe2,caffe2/caffe2,xzturn/caffe2