github/qemu: dump host kernel messages on QEMU or test failure

This can help to debug better a KVM failure like coconut-svsm#1081, since
KVM can print some more information in kernel logs.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

Author: stefano-garzarella

.github/workflows/qemu.yml

@@ -151,3 +151,7 @@ jobs:
             --nocc --timeout 180 \
             </dev/null 2>&1
 
+      - name: Dump host kernel messages on QEMU or test failure
+        if: failure()
+        run: sudo dmesg
+