CI Linux AppImage Docker: try also latest Ubuntu

.github/scripts/Linux/docker_appimage_tests.sh

@@ -3,9 +3,18 @@
 mkdir aitest-context # empty build context
 ./UltraGrid-"$VERSION"-x86_64.AppImage --appimage-extract
 
-for n in archlinux ubuntu; do
-        docker build -f .github/scripts/Linux/utils/Dockerfile.$n\
-         -t aitest-$n aitest-context
+for n in archlinux ubuntu:22.04 ubuntu:latest; do
+        dockerfile=.github/scripts/Linux/utils/Dockerfile.$n
+        if expr $n : ".*:"; then
+                image_name=$(echo $n | cut -d: -f 1)
+                image_version=$(echo $n | cut -d: -f 2)
+                n_dockerfile=$(mktemp)
+                cat .github/scripts/Linux/utils/Dockerfile."$image_name" |
+                        sed "s/DOCKER_IMAGE_VERSION/$image_version/"\
+                        > "$n_dockerfile"
+                dockerfile=$n_dockerfile
+        fi
+        docker build -f "$dockerfile" -t aitest-$n aitest-context
         docker run --rm -v "$PWD"/squashfs-root/:/AppImage aitest-$n sh -ce '
 /AppImage/AppRun -v
 /AppImage/AppRun --tool uv-qt -h

.github/scripts/Linux/utils/Dockerfile.ubuntu

@@ -1,6 +1,6 @@
 # inspired by https://github.com/aferrero2707/appimage-testsuite
 # installing libraries included in https://raw.githubusercontent.com/probonopd/AppImages/master/excludelist
-FROM ubuntu:22.04
+FROM ubuntu:DOCKER_IMAGE_VERSION
 RUN apt-get update
 RUN apt-get install -y libasound2 libegl1-mesa libfontconfig1 libgl1-mesa-glx \
     libgmp10 libharfbuzz0b libopengl0 libp11-kit0 libx11-6 xvfb