Change target platform to LINUX-OTHER

This is needed to be compatible with JDK 21+ which does not allow
other platforms (apart from the ones listed in the modules
plugin) when linking a system image.

Note the value of target platform doesn't matter to us, we just
choose a closest one to replace "android".

Bug: 313924276
Test: m EXPERIMENTAL_USE_OPENJDK21_TOOLCHAIN=true
Change-Id: Id805f31089fdbd78bf4db06c89ae391f25563448