Fixups for ESP32

Marlin/src/HAL/HAL_ESP32/HAL.h

@@ -55,9 +55,14 @@
 
 extern portMUX_TYPE spinlock;
 
-#define NUM_SERIAL 2
 #define MYSERIAL0 Serial
+
+#if ENABLED(WIFISUPPORT)
+  #define NUM_SERIAL 2
   #define MYSERIAL1 webSocketSerial
+#else
+  #define NUM_SERIAL 1
+#endif
 
 #define CRITICAL_SECTION_START portENTER_CRITICAL(&spinlock)
 #define CRITICAL_SECTION_END   portEXIT_CRITICAL(&spinlock)

Marlin/src/HAL/HAL_ESP32/WebSocketSerial.cpp

@@ -26,8 +26,10 @@
 #if ENABLED(WIFISUPPORT)
 
 #include "WebSocketSerial.h"
-#include "wifi.h"
 
+extern WebSocketSerial webSocketSerial;
+
+#include "wifi.h"
 #include <AsyncTCP.h>
 #include <ESPAsyncWebServer.h>
 

Marlin/src/pins/pins_ESP32.h

@@ -24,6 +24,10 @@
  * Espressif ESP32 (Tensilica Xtensa LX6) pin assignments
  */
 
+#ifndef ARDUINO_ARCH_ESP32
+  "Oops! Select an ESP32 board in 'Tools > Board.'"
+#endif
+
 #define BOARD_NAME "Espressif ESP32"
 
 //