accel/hvf: Build without target-specific knowledge Code in accel/ aims to be target-agnostic. Enforce that by moving the HVF file units to system_ss[], which is target-agnostic. Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20260225051303.91614-5-philmd@linaro.org>