Here is my jar, but I suspect that it is going to work for you too.
https://github.com/JohnRudolfLewis/n...ntcoreblah.jar
I believe there is a difference between our environments. On your Pi, when you run ldd libntcore.so, how does your output differ from mine below?
pi@raspberrypi:~ $ ldd libntcore.so
./libntcore.so: /usr/lib/arm-linux-gnueabihf/libstdc++.so.6: version `CXXABI_1.3.9' not found (required by ./libntcore.so)
./libntcore.so: /usr/lib/arm-linux-gnueabihf/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by ./libntcore.so)
linux-vdso.so.1 (0x7eded000)
/usr/lib/arm-linux-gnueabihf/libarmmem.so (0x76f6d000)
libstdc++.so.6 => /usr/lib/arm-linux-gnueabihf/libstdc++.so.6 (0x76e7a000)
libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0x76e4d000)
libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0x76d10000)
/lib/ld-linux-armhf.so.3 (0x54aef000)
libm.so.6 => /lib/arm-linux-gnueabihf/libm.so.6 (0x76c95000)