hmm, better luck with the .a extension but then:

OSError: cannot load library /home/travis/.cache/pants/bin/native-engine/linux/x86_64/9f290c431bae455b4ec49ee23fb071edb0eef136/native-engine: /home/travis/.cache/pants/bin/native-engine/linux/x86_64/9f290c431bae455b4ec49ee23fb071edb0eef136/native-engine: invalid ELF header