Added a build script for the Steam Deck AppImage.

tools/create_AppImage_SteamDeck.sh

@@ -0,0 +1,55 @@
+#!/usr/bin/bash
+#  SPDX-License-Identifier: MIT
+#
+#  EmulationStation Desktop Edition
+#  create_AppImage_SteamDeck.sh
+#
+#  Runs the complete process of building a Linux AppImage specific to the Valve Steam Deck.
+#
+#  This script has only been tested on Ubuntu 20.04 LTS.
+#
+
+echo "Building Steam Deck AppImage..."
+
+if [ ! -f .clang-format ]; then
+  echo "You need to run this script from the root of the repository."
+  exit
+fi
+
+if [ ! -f appimagetool-x86_64.AppImage ]; then
+  echo -e "Can't find appimagetool-x86_64.AppImage, downloading the latest version...\n"
+  wget "https://github.com/AppImage/AppImageKit/releases/download/continuous/appimagetool-x86_64.AppImage"
+fi
+
+chmod a+x appimagetool-x86_64.AppImage
+
+if [ ! -f linuxdeploy-x86_64.AppImage ]; then
+  echo -e "Can't find linuxdeploy-x86_64.AppImage, downloading the latest version...\n"
+  wget "https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage"
+fi
+
+chmod a+x linuxdeploy-x86_64.AppImage
+
+rm -rf ./AppDir
+mkdir AppDir
+
+rm -f CMakeCache.txt
+cmake -DSTEAM_DECK=on .
+make clean
+make -j8
+make install DESTDIR=AppDir
+cd AppDir
+ln -s usr/bin/emulationstation AppRun
+ln -s usr/share/pixmaps/emulationstation.svg .
+ln -s usr/share/applications/org.es_de.emulationstation-de.desktop .
+ln -s emulationstation.svg .DirIcon
+cd usr/bin
+ln -s ../share/emulationstation/resources .
+ln -s ../share/emulationstation/themes .
+cd ../../..
+
+./linuxdeploy-x86_64.AppImage -l /lib/x86_64-linux-gnu/libOpenGL.so.0 -l /lib/x86_64-linux-gnu/libgio-2.0.so.0 --appdir AppDir
+./appimagetool-x86_64.AppImage AppDir
+
+mv EmulationStation_Desktop_Edition-x86_64.AppImage EmulationStation-DE-x64_SteamDeck.AppImage
+echo -e "\nCreated AppImage EmulationStation-DE-x64_SteamDeck.AppImage"