Reinstate CONFIG_BT_NIMBLE_EXT_ADV as an option to fix redefinition.

Platformio adds the build flags to the command line and in the latest arduino
core, nimble is enabled so using MYNEWT_VAL_BLE_EXT_ADV will cause a redefinition
warning.

Author: h2zero

docs/Command_line_config.md

@@ -114,7 +114,9 @@ If defined, advertisement types will be printed as text while scanning in debug
 ## Extended advertising settings (ESP32C3, ESP32S3, ESP32H2 ONLY)
 
 `MYNEWT_VAL_BLE_EXT_ADV`  
-Set to 1 to enable extended advertising features
+Set to 1 to enable extended advertising features.
+For Platformio this may cause a redefinition warning with the latest arduino cores,
+to avoid this `CONFIG_BT_NIMBLE_EXT_ADV` can be used instead.
 
 `MYNEWT_VAL_BLE_MULTI_ADV_INSTANCES`  
 Sets the max number of extended advertising instances  

src/nimconfig.h

@@ -182,6 +182,11 @@
 
 #define MYNEWT_VAL_BLE_USE_ESP_TIMER (CONFIG_BT_NIMBLE_USE_ESP_TIMER)
 
+#ifdef CONFIG_BT_NIMBLE_EXT_ADV // Workaround for PlatformIO build flags causing redefinition warnings
+# undef MYNEWT_VAL_BLE_EXT_ADV
+# define MYNEWT_VAL_BLE_EXT_ADV (CONFIG_BT_NIMBLE_EXT_ADV)
+#endif
+
 #else // !ESP_PLATFORM
 # if defined(NRF51)
 #  include "syscfg/devcfg/nrf51cfg.h"