There is nothing special about this compile flag that doesn't mean we
can't just compute it with curr_cflags() which we should be using when
building a new set.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210224165811.11567-3-alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>