qapi_event_send_device_deleted is always included (together with the
rest of QAPI) in libqemuutil.a if either system-mode emulation or tools
are being built, and in that case the stub causes a duplicate symbol
to appear in libqemuutil.a.
Add the symbol only if events are not being requested.
Cc: qemu-stable@nongnu.org
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>