Increase the backend priority so that it's above random
Set has_backends to true so that meson doesn't complain when XLA is the only backend
Maybe downgrade pjrt_c_api.h to something lower than 0.40 so that it runs with older .so files, but it seems that 0.39 is the minimal one that has all features that we need, so maybe not worth it.
randomhas_backendsto true so that meson doesn't complain when XLA is the only backendpjrt_c_api.hto something lower than 0.40 so that it runs with older.sofiles, but it seems that 0.39 is the minimal one that has all features that we need, so maybe not worth it.