jruby: only wrap jruby executables

Other executables all invoke jruby, and so don't need to be wrapped.

In some cases wrapping breaks the executables because one file is a ruby
script that directly loads the other (e.g. `gem` is a wrapper that loads
`jgem`).  In this case, if the latter script has been wrapped by nix,
loading will fail.

pkgs/development/interpreters/jruby/default.nix

@@ -18,7 +18,7 @@ stdenv.mkDerivation rec {
      rm $out/bin/*.{bat,dll,exe,sh}
      mv $out/COPYING $out/LICENSE* $out/docs
 
-     for i in $out/bin/*; do
+     for i in $out/bin/jruby{,.bash}; do
        wrapProgram $i \
          --set JAVA_HOME ${jre}
      done