Add "runtime." prefix to "build_properties_custom.*" preferences

Author: sandeepmistry

arduino-core/src/cc/arduino/Compiler.java

@@ -228,7 +228,7 @@ private void callArduinoBuilder(TargetBoard board, TargetPlatform platform, Targ
     commandLine.addArgument("-warnings=" + PreferencesData.get("compiler.warning_level"), false);
 
     PreferencesData.getMap()
-      .subTree("build_properties_custom")
+      .subTree("runtime.build_properties_custom")
       .entrySet()
       .stream()
       .forEach(kv -> commandLine.addArgument("-prefs=\"" + kv.getKey() + "=" + kv.getValue() + "\"", false));

arduino-core/src/processing/app/helpers/CommandlineParser.java

@@ -277,7 +277,7 @@ private void processPrefArgument(String arg) {
       BaseNoGui.showError(null, I18n.format(tr("{0}: Invalid argument to --pref, should be of the form \"pref=value\""), arg), 3);
 
     PreferencesData.set(split[0], split[1]);
-    PreferencesData.set("build_properties_custom." + split[0], split[1]);
+    PreferencesData.set("runtime.build_properties_custom." + split[0], split[1]);
   }
 
   public boolean isDoVerboseBuild() {