Fix LookAndFeel loader

Fix arduino#8119
Close arduino#8122

Author: cmaglie

arduino-core/src/processing/app/linux/Platform.java

@@ -37,10 +37,9 @@
  */
 public class Platform extends processing.app.Platform {
 
-  // TODO Need to be smarter here since KDE people ain't gonna like that GTK.
-  //      It may even throw a weird exception at 'em for their trouble.
   @Override
   public void setLookAndFeel() throws Exception {
+    super.setLookAndFeel();
     GTKLookAndFeelFixer.installGtkPopupBugWorkaround();
   }
 

build/linux/dist/arduino

@@ -25,7 +25,7 @@ if [ -x "$APPDIR/java/bin/java" ]; then
 fi
 
 # Collect options to java in an array, to properly handle whitespace in options
-JAVA_OPTIONS=("-DAPP_DIR=$APPDIR" "-Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel")
+JAVA_OPTIONS=("-DAPP_DIR=$APPDIR")
 
 # Only show the splash screen when no options are present
 if [[ "$@" != *"--"* ]] ; then