lwip: Define LWIP_ESP8266 in port lwipopts.h not gcc command line

components/lwip/component.mk

@@ -6,6 +6,6 @@ COMPONENT_ADD_INCLUDEDIRS := include/lwip include/lwip/port
 
 COMPONENT_SRCDIRS := api apps/sntp apps core/ipv4 core/ipv6 core netif port/freertos port/netif port
 
-EXTRA_CFLAGS := -Wno-error=address -Waddress -DLWIP_ESP8266
+EXTRA_CFLAGS := -Wno-error=address -Waddress
 
 include $(IDF_PATH)/make/component_common.mk

components/lwip/include/lwip/port/lwipopts.h

@@ -34,6 +34,8 @@
 
 #include <stdlib.h>
 
+/* Enable all Espressif-only options */
+#define LWIP_ESP8266
 
 /*
    -----------------------------------------------

components/tcpip_adapter/component.mk

@@ -2,6 +2,4 @@
 # Component Makefile
 #
 
-EXTRA_CFLAGS := -DLWIP_ESP8266
-
 include $(IDF_PATH)/make/component_common.mk