This is 32-bit Zero PPC build, not PPC64 that is already handled.

```
=== Output from failing command(s) repeated here ===
* For target support_images_jdk__jlink_jdk_exec:
Error: unknown target platform linux-ppc
java.io.IOException: unknown target platform linux-ppc
at jdk.jlink/jdk.tools.jlink.internal.JlinkTask.targetPlatform(JlinkTask.java:647)
at jdk.jlink/jdk.tools.jlink.internal.JlinkTask.createImageProvider(JlinkTask.java:569)
at jdk.jlink/jdk.tools.jlink.internal.JlinkTask.createImage(JlinkTask.java:410)
at jdk.jlink/jdk.tools.jlink.internal.JlinkTask.run(JlinkTask.java:285)
at jdk.jlink/jdk.tools.jlink.internal.Main.run(Main.java:56)
at jdk.jlink/jdk.tools.jlink.internal.Main.main(Main.java:34)
```