accel/tcg: Move curr_cflags into cpu-exec.c

accel/tcg: Move curr_cflags into cpu-exec.c

We will shortly have more than a simple member read here,
with stuff not necessarily exposed to exec/exec-all.h.

Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210717221851.2124573-3-richard.henderson@linaro.org>