exec: Restrict inclusion of 'user/guest-base.h'

exec: Restrict inclusion of 'user/guest-base.h'

Declare 'have_guest_base' in "user/guest-base.h".

Very few files require this header, so explicitly include
it there instead of "exec/cpu-all.h" which is used in many
source files.

Assert this user-specific header is only included from user
emulation.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20231211212003.21686-23-philmd@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>