error: "Unsupported platform: unknown-darwin" when using JRuby's ffi and Java 1.7 macosx-port build

Using JRuby built-in ffi and a recent macosx-port Java 1.7 build generates an: "Unsupported platform: unknown-darwin" error.

Seems like the builds report their platform as "unknown-darwin". Also looks like an interaction with JRubies built-in ffi support.

Details ...

I installed jruby head using rvm using the standard Java 1.6.0_24 on Mac OS X 10.6.7

Then using a recent build of the macosx-port Java 1.7 build:

http://www.concord.org/~sbannasch/macosx-port/java-1.7.0-internal-macosx-port-2011-04-25.tar.gz
Expand and copy to ~/Library/Java/JavaVirtualMachines
Open /Applications/Utilities/Java\ Preferences.app and move OpenJDK7 to the top of the list.

Note: this is not an mlvm build – just the macosx-port version based off of the bsd-port.

Now open a new shell.

$ java -version
openjdk version "1.7.0-internal"
OpenJDK Runtime Environment (build 1.7.0-internal-stephen_2011_04_16_22_03-b00)
OpenJDK 64-Bit Server VM (build 21.0-b07, mixed mode)

$ ruby --version
jruby 1.6.1 (ruby-1.8.7-p330) (2011-04-25 ef0212b) (OpenJDK 64-Bit Server VM 1.7.0-internal) [darwin-universal-java]

I then also installed rubygems 1.7.2 (but I don't think that matters):