Don't export sketch if the underlying core does not support it. Fixes #3171

Author: Federico Fissore

arduino-core/src/processing/app/debug/Compiler.java

@@ -1155,6 +1155,11 @@ void runRecipe(String recipe) throws RunnerException, PreferencesMapException {
 
   //7. Save the .hex file
   void saveHex() throws RunnerException {
+    if (!prefs.containsKey("recipe.output.tmp_file") || !prefs.containsKey("recipe.output.save_file")) {
+      System.err.println(_("Warning: This core does not support exporting sketches. Please consider upgrading it or contacting its author"));
+      return;
+    }
+
     PreferencesMap dict = new PreferencesMap(prefs);
     dict.put("ide_version", "" + BaseNoGui.REVISION);