linux-x86_64-qt5: Install squashfs-tools for mksquashfs

Author: kazarmy

.github/actions/build-linux-old/entrypoint.sh

@@ -40,7 +40,8 @@ apt-get -y install libgraphviz-dev \
     libpcre2-dev \
     libfuse2 \
     pkg-config \
-    git
+    git \
+    squashfs-tools
 
 
 if [ "$image" = "ubuntu:18.04" ]; then
@@ -196,4 +197,4 @@ then
     echo PACKAGE_PATH=build/$APPIMAGE_FILE >> $GITHUB_ENV
     echo PACKAGE_PATH=build/$APPIMAGE_FILE >> $GITHUB_OUTPUT
     echo UPLOAD_ASSET_TYPE=application/x-executable >> $GITHUB_ENV
-fi
+fi