Linux: arduino startup script needs "" around $CURDIR, otherwise

it will fail when folders have spaces. Found in a comment at #2982

Author: Federico Fissore

Diff for: build/linux/dist/arduino

@@ -33,4 +33,4 @@ if [ -x ./java/bin/java ]; then
   JAVA=./java/bin/java
 fi
 
-$JAVA -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel $SPLASH processing.app.Base --curdir $CURDIR "$@"
+$JAVA -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel $SPLASH processing.app.Base --curdir "$CURDIR" "$@"