chore: add ubuntu:26.04 arm to build matrix

Author: Julusian

.github/workflows/linux-system.yml

@@ -23,6 +23,11 @@ jobs:
                       container: ubuntu:26.04
                       apt_prefix: ""
                       upload_artifacts: false
+                    - os: ubuntu-24.04-arm
+                      distribution: resolute
+                      container: ubuntu:26.04
+                      apt_prefix: ""
+                      upload_artifacts: false
 
         runs-on: ${{ matrix.os }}
         container: ${{ matrix.container }}
@@ -73,7 +78,7 @@ jobs:
                   # Download required packages
                   cd ..
                   apt-get download casparcg-cef-142=$CASPARCG_CEF_VER
-                  apt-get download casparcg-scanner
+                  apt-cache show casparcg-scanner &>/dev/null && apt-get download casparcg-scanner || true
               env:
                   CI: 1
                   DEBIAN_FRONTEND: noninteractive