Experiment: C++17 support (#9874)

* Add C++17 support

* Add C++17 runtime probes and update build configurations for STM32 and Portduino

* Remove unflags

* Update C++ standard flags across the platforms

* Convert a couple of instances to structured bindings

* NRF52 platform.txt to add C++17 support

* Still need the unflags apparently

* Remove C++17 runtime probe tests from test_main.cpp

* Reconfigured doesnt need a nodiscard

* Remove nodiscard attribute from init() method in RadioInterface

* Remove mbedtls/error.h from build flags

Removed include directive for mbedtls/error.h from build flags.

* Fix IRAM overflow

* Fix IRAM overflow

* Add build flag to exclude MQTT from rak11200

* Update C++ standard from gnu17 to gnu++17

variants/esp32/esp32-common.ini

@@ -27,7 +27,12 @@ board_build.filesystem = littlefs
 # Remove -DMYNEWT_VAL_BLE_HS_LOG_LVL=LOG_LEVEL_CRITICAL for low level BLE logging.
 # See library directory for BLE logging possible values: .pio/libdeps/tbeam/NimBLE-Arduino/src/log_common/log_common.h
 # This overrides the BLE logging default of LOG_LEVEL_INFO (1) from: .pio/libdeps/tbeam/NimBLE-Arduino/src/esp_nimble_cfg.h
-build_unflags = -fno-lto
+build_unflags =
+  -fno-lto
+  # Keep explicit std unflags on ESP32; base-level unflags are not sufficient
+  # to prevent framework-injected C++11 fallback on this platform.
+  -std=c++11
+  -std=gnu++11
 build_flags =
   ${arduino_base.build_flags}
   -flto
@@ -35,7 +40,7 @@ build_flags =
   -Wextra
   -Isrc/platform/esp32
   -include mbedtls/error.h
-  -std=c++11
+  -std=gnu++17
   -DLOG_LOCAL_LEVEL=ESP_LOG_DEBUG
   -DCORE_DEBUG_LEVEL=ARDUHAL_LOG_LEVEL_DEBUG
   -DMYNEWT_VAL_BLE_HS_LOG_LVL=LOG_LEVEL_CRITICAL

variants/esp32/rak11200/platformio.ini

@@ -16,4 +16,8 @@ build_flags =
   ${esp32_base.build_flags}
   -D RAK_11200
   -I variants/esp32/rak11200
+  -DMESHTASTIC_EXCLUDE_WEBSERVER=1
+  -DMESHTASTIC_EXCLUDE_PAXCOUNTER=1
+  -DMESHTASTIC_EXCLUDE_RANGETEST=1
+  -DMESHTASTIC_EXCLUDE_MQTT=1
 upload_speed = 115200