Preserve boards.txt custom menu order.

Fix #7955

Author: cmaglie

app/src/processing/app/Base.java

@@ -1432,7 +1432,7 @@ public void actionPerformed(ActionEvent actionevent) {
     boardMenu.add(new JSeparator());
 
     // Generate custom menus for all platforms
-    Set<String> customMenusTitles = new HashSet<>();
+    Set<String> customMenusTitles = new LinkedHashSet<>();
     for (TargetPackage targetPackage : BaseNoGui.packages.values()) {
       for (TargetPlatform targetPlatform : targetPackage.platforms()) {
         customMenusTitles.addAll(targetPlatform.getCustomMenus().values());