Producing "bundled" JREs for other platforms?

[org.openjdk at io7m.com]

Hello.

I understand that in JDK 9, the "jlink" tool is able to produce a
run-time image that contains the application's modules and a bundled
JRE (which is itself stripped down to only those modules required to
actually run the application). Unless I've misunderstood, this seems to
imply that there'd be a small set of platform-specific native
executables capable of executing the bundled runtime (I'm not sure
what else it could mean).

I can't seem to find anything conclusive online, so I have to ask: Am I
required to build images on each of the platforms I support? Currently,
I distribute code which I expect to run on Windows, Linux, OS X,
Solaris, and FreeBSD, on a number of architectures for each. I only ever
actually *build* code on Linux AMD64, which saves me from having one
trusted build setup for each combination of operating system and
architecture (I can run the tests on any untrusted system).

If the tool is capable of producing runtimes for other platforms: Who
defines for which platforms the tool is capable of doing so?

Is there more documentation on jlink available? The only notes I can
find are JEP-282 and bug JDK-8080531. I'm using what appears to be
early access build 128 and the jlink program included with that seems
to be somewhat light on command line arguments that could suggest that
it can do any of the above.

Regards,
Mark