Facing issue in loading Ethernet Interface for Raspberry Pi 3 B+ buildroot

Question

I am building a Custom OS using Buildroot. I am following this article to build the custom os.

Author of that article gave a sample image of the os that will be created after the build is completed. I downloaded the Os image and flashed it on the SD card, in that case, I was able to load the ethernet interface for Raspberry Pi.

But When I started to build using the jumpnow_rpi3_defconfig given by the author using buildroot tool for Raspberry Pi I am unable to load the ethernet interface.

Steps I have followed are =>

git clone -b jumpnow https://github.com/jumpnow/buildroot
cd buildroot
make jumpnow_rpi3_defconfig
make

Booting logs related to Ethernet Interface =>

Starting network: [    3.492149] usb 1-1.1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
Waiting for interface eth0 to appear[    3.705901] brcmfmac: brcmf_c_preinit_dcmds: Firmware version = wl0: Feb 27 2018 03:15:32 version 7.45.154 (r684107 CY) FWID 01-4fbe0b04
[    3.724048] brcmfmac: brcmf_c_preinit_dcmds: CLM version = API: 12.2 Data: 9.10.105 Compiler: 1.29.4 ClmImport: 1.36.3 Creation: 2018-03-09 18:56:28
[    3.769867] lan78xx 1-1.1.1:1.0 (unnamed net_device) (uninitialized): can't register MDIO bus
[    3.783944] lan78xx 1-1.1.1:1.0 (unnamed net_device) (uninitialized): MDIO INIT FAILED.....
[    3.798153] lan78xx 1-1.1.1:1.0 (unnamed net_device) (uninitialized): Bind routine FAILED
[    3.817634] random: crng init done
[    3.824167] random: 2 urandom warning(s) missed due to ratelimiting
............... timeout!
run-parts: /etc/network/if-pre-up.d/wait_iface: exit status 1
FAIL

Output of ifconfig -a =>

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:512 errors:0 dropped:0 overruns:0 frame:0
          TX packets:512 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:37888 (37.0 KiB)  TX bytes:37888 (37.0 KiB)

wlan0     Link encap:Ethernet  HWaddr B8:27:EB:44:DB:B4
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

Output of ifup eth0 =>

# ifup eth0
Waiting for interface eth0 to appear............... timeout!
run-parts: /etc/network/if-pre-up.d/wait_iface: exit status 1

Kernel version =>

# uname -r
4.14.98-v7

What am I missing here or doing wrong here?