native-lib-loader option instead of using narSystem.

When we have <narSystemPackage>native-lib-loader</narSystemPackage>, we copy the output to /META-INF/lib according to native-lib-loader convention.

The minimal project for testing it is https://github.com/hkmoon/nar-native-lib.

rephrase to "Then, the NAR plugin..."

Also, this comes off as sounding circular to me. You generate a NarSystem class, which will create a JNI interface with the help of the NarSystem class? Could this process be clarified a bit?