Unable to build openbmc-1-0.91-151

[ManshiMuskan]

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Unexpected behavior you saw
These are the error and warning I am getting while building this opembmc version

WARNING: Host distribution "ubuntu-20.04" has not been validated with this version of the build system; you may possibly experience unexpected failures. It is recommended that you use a tested distribution.
WARNING: /home/cdac/Downloads/openbmc-1-0.91-151/meta/recipes-core/os-release/os-release.bb: Unexpected exception from 'git' call: Execution of 'export PSEUDO_DISABLED=1; git --work-tree /home/cdac/Downloads/openbmc-1-0.91-151 --git-dir /home/cdac/Downloads/openbmc-1-0.91-151/.git describe --dirty' failed with exit code 128:
fatal: not a git repository: '/home/cdac/Downloads/openbmc-1-0.91-151/.git'
ERROR: Failed to parse recipe: /home/cdac/Downloads/openbmc-1-0.91-151/meta/recipes-core/os-release/os-release.bb

OpenBMC Information:

• /etc/os-release:
• uname -a:
• Any additional patches or changes:

Additional context
Add any other context about the problem here.