LF clock compiler warning when compiling for arduino:mbed_nano:nano33ble (v4.2.1)

[zfields]

#warning No configuration for LF clock source. Xtal source will be used as a default configuration.

I have always compiled with -Werror. I have not changed my source code. I have only upgraded my Arduino CLI from 0.34.2 to 1.1.1, and this #warning has now appeared.

In file included from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/TARGET_MCU_NRF52840/config/sdk_config.h:11967:0,
/home/blues/.arduino15/packages/arduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -c -Wall -Wextra -g3 -nostdlib @/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/variants/ARDUINO_NANO33BLE/defines.txt @/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/variants/ARDUINO_NANO33BLE/cxxflags.txt -DARDUINO_ARCH_NRF52840 -MMD -mcpu=cortex-m4 -mfloat-abi=softfp -mfpu=fpv4-sp-d16 -DARDUINO=10607 -DARDUINO_ARDUINO_NANO33BLE -DARDUINO_ARCH_MBED_NANO -DARDUINO_ARCH_MBED -DARDUINO_LIBRARY_DISCOVERY_PHASE=0 -I/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino -I/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/variants/ARDUINO_NANO33BLE -Wno-unused-parameter -Werror -I/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/api/deprecated -I/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/api/deprecated-avr-comp -iprefix/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino @/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/variants/ARDUINO_NANO33BLE/includes.txt /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/api/CanMsg.cpp -o /home/blues/.cache/arduino/sketches/CAC5CD9D43929367233EF06CE5385189/core/api/CanMsg.cpp.o
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/integration/nrfx/nrfx_config.h:45,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/modules/nrfx/nrfx.h:44,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/modules/nrfx/hal/nrf_gpio.h:44,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/TARGET_MCU_NRF52840/TARGET_ARDUINO_NANO33BLE/PinNames.h:23,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/objects.h:45,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/TARGET_MCU_NRF52840/TARGET_ARDUINO_NANO33BLE/device.h:37,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/hal/include/hal/trng_api.h:24,
                 from /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/WMath.cpp:26:
/home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/nrf5x_lf_clk_helper.h:43:6: error: #warning No configuration for LF clock source. Xtal source will be used as a default configuration. [-Werror=cpp]
     #warning No configuration for LF clock source. Xtal source will be used as a default configuration.
      ^~~~~~~
cc1plus: all warnings being treated as errors

Using library Blues Wireless Notecard at version 1.6.3 in folder: /home/blues/Arduino/libraries/Blues_Wireless_Notecard 
Using library Wire in folder: /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/libraries/Wire (legacy)
Error during build: exit status 1

Used library            Version Path
Blues Wireless Notecard 1.6.3   /home/blues/Arduino/libraries/Blues_Wireless_Notecard
Wire                            /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1/libraries/Wire

Used platform     Version Path
arduino:mbed_nano 4.2.1   /home/blues/.arduino15/packages/arduino/hardware/mbed_nano/4.2.1
Error: Process completed with exit code 1.