librealsense: "Failed to identify Internet connection" but connection works

Required Info
Camera Model	D435
Firmware Version	05.11.01.100 prior to failure
Operating System & Version	Ubuntu 16.04
Kernel Version (Linux Only)	4.8.15-rt10 PREEMPT RT
SDK Version	2.22.0 prior to failure
Language	C++
Segment	Robot

Issue Description

After updating to master, I tried to rebuild from scratch and I’m seeing this:

<path>/librealsense/build$ cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo 
-- The CXX compiler identification is GNU 7.4.0
-- The C compiler identification is GNU 7.4.0
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
CMake Error at CMake/connectivity_check.cmake:3 (file):
  file DOWNLOAD cannot open file for write.
Call Stack (most recent call first):
  CMakeLists.txt:5 (include)


-- Failed to identify Internet connection
-- Info: REALSENSE_VERSION_STRING=2.24.0
-- Performing Test COMPILER_SUPPORTS_CXX11
-- Performing Test COMPILER_SUPPORTS_CXX11 - Success
-- Performing Test COMPILER_SUPPORTS_CXX0X
-- Performing Test COMPILER_SUPPORTS_CXX0X - Success
-- Setting Unix configurations
-- No internet connection, disabling BUILD_WITH_TM2
-- using RS2_USE_V4L2_BACKEND
-- Found usb: /usr/lib/x86_64-linux-gnu/libusb-1.0.so  
-- GLFW 3.3 not found; using internal version
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for pthread_create
-- Looking for pthread_create - found
-- Found Threads: TRUE  
-- Could NOT find Vulkan (missing: VULKAN_LIBRARY VULKAN_INCLUDE_DIR) 
-- Using X11 for window creation
-- Looking for XOpenDisplay in /usr/lib/x86_64-linux-gnu/libX11.so;/usr/lib/x86_64-linux-gnu/libXext.so
-- Looking for XOpenDisplay in /usr/lib/x86_64-linux-gnu/libX11.so;/usr/lib/x86_64-linux-gnu/libXext.so - found
-- Looking for gethostbyname
-- Looking for gethostbyname - found
-- Looking for connect
-- Looking for connect - found
-- Looking for remove
-- Looking for remove - found
-- Looking for shmat
-- Looking for shmat - found
-- Looking for IceConnectionNumber in ICE
-- Looking for IceConnectionNumber in ICE - found
-- Found X11: /usr/lib/x86_64-linux-gnu/libX11.so
-- Found OpenGL: /usr/lib/x86_64-linux-gnu/libGL.so   
-- No internet connection, disabling IMPORT_UVC_FW
-- Configuring incomplete, errors occurred!
See also "<path>/librealsense/build/CMakeFiles/CMakeOutput.log".

The internet connection is definitely working (I’m posting this issue) and I don’t get why internet absence would want to kill the build since the firmware update could be done at a separate moment.

Commenting this line results in

<path>/librealsense/common/fw-update-helper.cpp:15:10: fatal error: common/fw/D4XX_FW_Image.h: No such file or directory
 #include "common/fw/D4XX_FW_Image.h"
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

which is included due to #ifdef INTERNAL_FW which I can’t find being defined anywhere, and I also can’t find the to-be-included file: the closest match is D4XX_FW_Image.rc which also doesn’t exist but is included in here.