execute previous tests successfully
the JNI part can be built and tested by simply doing
```
$ ./autogen.sh
$ ./configure --enable-jni --enable-experimental --enable-module-ecdh
$ make
$ javac src/java/org/bitcoin/*
$ java -Djava.library.path=.libs -cp src/java org.bitcoin.NativeSecp256k1Test check-java
```
Once https://reviews.bitcoinabc.org/D2686 is passed we can do this automatically