Triplicate BouncyCastle jars in the build

Hi!

At least two versions of the jars end up in the distribution.

```
$ find . -name *bc*.jar
./ext/openssl/lib/bcpkix-jdk15on-1.47.jar
./ext/openssl/lib/bcprov-jdk15on-1.47.jar
./lib/ruby/shared/bcpkix-jdk15on-1.47.jar
./lib/ruby/shared/bcpkix-jdk15on-147.jar
./lib/ruby/shared/bcprov-jdk15on-1.47.jar
./lib/ruby/shared/bcprov-jdk15on-147.jar
```
