Build error when using external toolchain in Buildroot

Question

I am trying to use externel toolchain option in Buildroot and to use gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.gz as external toolchain. I am following the steps mentioned in Buildroot manual section 6.1.3. I already have the toolchain tarball so I did not do make sdk part. In the menuconfig I have specified like below:

1. Set Toolchain type to External toolchain
2. Set Toolchain to Custom toolchain
3. Set Toolchain origin to Toolchain to be downloaded and installed
4. Set Toolchain URL to file:///path/to/your/sdk/tarball.tar.gz : In my case I have set it to file:////root/br-tcg4/tmp/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.gz

Then when I do make I get below errors:

.
.
.
Unpacking toolchain to "/root/br-tcg4/bat/buildscripts/../../tmp/toolchain" ...
done

Current STW RootFs version: "STW-V4.00r1"
Have you updated the version? Do you want to continue? [Y/n] Y
Make rfs ...
make: Entering directory '/root/br-tcg4/libs/br_pjt'
Makefile:1051: warning: overriding recipe for target '/root/br-tcg4/libs/br_pjt/output/staging'
Makefile:475: warning: ignoring old recipe for target '/root/br-tcg4/libs/br_pjt/output/staging'
/usr/bin/make -j1 O=/root/br-tcg4/libs/br_pjt/output HOSTCC="/usr/bin/gcc" HOSTCXX="/usr/bin/g++" syncconfig
make[1]: Entering directory '/root/br-tcg4/libs/br_pjt'
make[1]: Leaving directory '/root/br-tcg4/libs/br_pjt'
tar-1.29.cpio.gz: OK (sha256: 9173f222464dd3676118408840da5990527062b5c7daf6487bed7c396c45bfb1)
>>> toolchain-external-custom  Downloading
cp: cannot stat '/root/br-tcg4/tmp/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.gz': No such file or directory
--2022-02-01 20:02:13--  http://sources.buildroot.net/toolchain-external-custom/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.gz
Resolving sources.buildroot.net (sources.buildroot.net)... 172.67.72.56, 104.26.1.37, 104.26.0.37, ...
Connecting to sources.buildroot.net (sources.buildroot.net)|172.67.72.56|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2022-02-01 20:02:14 ERROR 404: Not Found.

--2022-02-01 20:02:14--  http://sources.buildroot.net/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.gz
Resolving sources.buildroot.net (sources.buildroot.net)... 172.67.72.56, 104.26.1.37, 104.26.0.37, ...
Connecting to sources.buildroot.net (sources.buildroot.net)|172.67.72.56|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2022-02-01 20:02:14 ERROR 404: Not Found.

make: *** [package/pkg-generic.mk:171: /root/br-tcg4/libs/br_pjt/output/build/toolchain-external-custom/.stamp_downloaded] Error 1
make: Leaving directory '/root/br-tcg4/libs/br_pjt'

------------- Error occured! -------------

When I checked http://sources.buildroot.net/toolchain-external-custom there is no file gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.gz.

Can anyone please let me know how to properly use external toolchain option in Buildroot?

Your help will be much appreciated.

Thanks in advance

P.S: I am using Buildroot 2020.02.12 and Ubuntu 20.04 as build system. please let me know if any info is missing here.