add disable_spire build tag for entrypoint command

[jkhelil]

We need to make Tekton Pipelines FIPS compliant, and the entrypoint command is a key step in this effort. Since it is statically compiled, we must ensure that cryptographic symbols are removed from the entrypoint binary. To achieve this, we need compile options to disable TLS, SPIRE, and any network-related functionality.

This PR is a partial implementation that introduces a build tag to disable SPIRE (github.com/tektoncd/pipeline/pkg/spire) in cmd/entrypoint/main.go.

Changes

This PR introduces a build tag to conditionally disable SPIRE functionality in the cmd/entrypoint/main.go file. The following changes have been made:

• Added a build tag disable_spire to conditionally exclude SPIRE-related logic.
• Split SPIRE logic into two files:
  spire.go for when SPIRE is enabled.
  spire_disabled.go for when SPIRE is disabled using the disable_spire build tag.

partially fixes #8531

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• Has Docs if any changes are user facing, including updates to minimum requirements e.g. Kubernetes version bumps
• Has Tests included if any functionality added or changed
• pre-commit Passed
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• Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

NONE

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[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[afrittoli]

fixes #8531

This comment will close the issue once this PR is merged, but it only addresses one part of the issue.
It's better to use "partially-fixes" in this case, or "related to"

[afrittoli]

Thanks for this.
I think it needs some documentation:

• dev docs explaining how to build with spire disabled
• end user docs, in the spire section, explaining tha spire needs to be enabled at build time for the config flag to actually work

Would it make sense to log something or fail if the spire flag was enabled when using a build without spire?

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[jkhelil]

@afrittoli @vdemeester I have added docs and check enable_spire flag to exit if the build is not spire enabled

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
cmd/entrypoint/main.go	11.9%	12.5%	0.6
cmd/entrypoint/spire.go	Do not exist	0.0%
pkg/entrypoint/entrypointer.go	88.1%	88.0%	-0.0
pkg/entrypoint/spire.go	Do not exist	100.0%

[vdemeester]

/kind cleanup
/retest