Fix QEMU E2E test: make kernel image readable

Ubuntu 24.04 installs kernel images with restrictive permissions
(0600/0640), causing QEMU to fail with "Permission denied" when
opening /boot/vmlinuz-*.

Author: xaionaro@dx.center

.github/workflows/ci.yml

@@ -59,6 +59,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y qemu-system-x86 linux-image-generic
+          sudo chmod +r /boot/vmlinuz-*
 
       - name: Run QEMU E2E tests
         run: make test-qemu