SH_EXT_STDOUT_STDERR is a v2.0 semihosting extension: the guest
can open ":tt" with a file mode requesting append access in
order to open stderr, in addition to the existing "open for
read for stdin or write for stdout". Implement this and
report it via the :semihosting-features data.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20190916141544.17540-16-peter.maydell@linaro.org
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