cmake: add support for missing SOVERSION (#919)
cmake: add support for missing SOVERSION (#919)

Summary:
Closes: https://github.com/facebookresearch/fastText/issues/918
Pull Request resolved: https://github.com/facebookresearch/fastText/pull/919

Reviewed By: EdouardGrave, tscmoo

Differential Revision: D17737704

Pulled By: Celebio

fbshipit-source-id: 3bc0c4825917017d4f98fa4c8c3f1af2a0c8c31f

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