Add LinkRuntimeFiles.sh scripts in GDJS to ease development of the game engine

The script allow to quickly link the sources of the game engine in a folder
of an exported/previewed game, so that any change in the game engine can
be tested directly in the game.

GDJS/scripts/LinkRuntimeFiles.sh

@@ -0,0 +1,39 @@
+# Make links to the GDJS runtime files and extensions in the specified directory.
+# Useful for working on the game engine:
+# - First export your game/preview in a directory
+# - Then launch ./LinkRuntimeFiles /path/to/the/export/dir
+# - You can then modify the game engine files and test your changes directly in the game
+
+if [ $# -eq 0 ]; then
+	echo "You must specify the directory where the symbolic links should be created"
+  exit
+fi
+
+DESTINATION=$1
+RUNTIME_SOURCE=$(pwd)/../Runtime
+
+#Instead of removing directories, keep a backup of them in case
+rm_destination_with_BACKUP() {
+  if [ -d $DESTINATION/$1 ]; then
+    if [ ! -d $DESTINATION/BACKUP-$1 ]; then
+      mv -f $DESTINATION/$1 $DESTINATION/BACKUP-$1
+    fi
+    rm -rf $DESTINATION/$1
+  fi
+}
+
+#Remove all sub-directories that are going to be replaced by links
+for D in `find $RUNTIME_SOURCE -type d -depth 1`
+do
+  if [ $D != $RUNTIME_SOURCE ]; then
+    NAME=`basename $D`
+    rm_destination_with_BACKUP $NAME
+  fi
+done
+rm_destination_with_BACKUP "Extensions"
+
+#Link all runtime files and directories
+ln -s -f -F $RUNTIME_SOURCE/* $DESTINATION
+
+#Link Extensions directory
+ln -s -f -F $(pwd)/../../Extensions $DESTINATION