target/rx: Ensure not being build on user emulation

Currently only system emulation is supported.
Assert no target code is built for user emulation.
Remove #ifdef'ry since more work is required before
being able to emulate a user process.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20250121142341.17001-3-philmd@linaro.org>
3 files changed