[build] Fix rules/functions generate_manifest function

[liushilongbuaa]

Why I did it

Fix a bug in sonic debug image build. That bug is imported in the following PR:
#8920

How I did it

How to verify it

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106

Description for the changelog

A picture of a cute animal (not mandatory but encouraged)

[stepanblyschak]

@liushilongbuaa What is the issue?

[liushilongbuaa]

@liushilongbuaa What is the issue?

@stepanblyschak Official debug sonic image build break.
generate_manifest uses 'j2 $($*.gz_PATH)/Dockerfile$(2).j2' command to generate Dockerfile.
If replace '-dbg' with 'dbg', j2 can't find correct Template file.

[stepanblyschak]

I think j2 $($*.gz_PATH)/Dockerfile$(2).j2 in generate_manifest was a copy paste mistake. The generate_manifest should not generate the Dockerfile. The Dockerfile is generated by slave.mk https://github.com/Azure/sonic-buildimage/blob/master/slave.mk#L814 and for debug dockers - https://github.com/Azure/sonic-buildimage/blob/master/slave.mk#L871. I suggest just to remove the line j2 $($*.gz_PATH)/Dockerfile$(2).j2.

[liushilongbuaa]

@stepanblyschak I think you are right. I triggered a job to validate this PR. https://dev.azure.com/mssonic/build/_build/results?buildId=53359&view=results
build failed, but it is related to another issue #9305

[xumia]

It is failed in publishing the artifacts step in the second attempt (error message: [error]Artifact sonic-buildimage.vs already exists for build 53358.), it will be fixed in another PR #9357, skip the merge validation checks and force merged it to break the loop.