tests/check-block.sh: Refuse to run the iotests with BusyBox' sed

BusyBox' sed reports itself as "This is not GNU sed version 4.0"
when being run with the --version parameter. However, the iotests
really need GNU sed, they do not work with the BusyBox version.
So let's make sure that we really have GNU sed and refuse to run
the tests with BusyBox' sed.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20210119134749.401311-1-thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/check-block.sh

@@ -60,6 +60,13 @@ if ! (sed --version | grep 'GNU sed') > /dev/null 2>&1 ; then
         echo "GNU sed not available ==> Not running the qemu-iotests."
         exit 0
     fi
+else
+    # Double-check that we're not using BusyBox' sed which says
+    # that "This is not GNU sed version 4.0" ...
+    if sed --version | grep -q 'not GNU sed' ; then
+        echo "BusyBox sed not supported ==> Not running the qemu-iotests."
+        exit 0
+    fi
 fi
 
 cd tests/qemu-iotests