Extended build failure logging

[PawelWMS]

Merge Checklist

All boxes should be checked before merging the PR (just tick any boxes which don't apply to this PR)

• The toolchain has been rebuilt successfully (or no changes were made to it)
• The toolchain/worker package manifests are up-to-date
• Any updated packages successfully build (or no packages were changed)
• Packages depending on static components modified in this PR (Golang, *-static subpackages, etc.) have had their Release tag incremented.
• Package tests (%check section) have been verified with RUN_CHECK=y for existing SPEC files, or added to new SPEC files
• All package sources are available
• cgmanifest files are up-to-date and sorted (./cgmanifest.json, ./toolkit/scripts/toolchain/cgmanifest.json, .github/workflows/cgmanifest.json)
• LICENSE-MAP files are up-to-date (./SPECS/LICENSES-AND-NOTICES/data/licenses.json, ./SPECS/LICENSES-AND-NOTICES/LICENSES-MAP.md, ./SPECS/LICENSES-AND-NOTICES/LICENSE-EXCEPTIONS.PHOTON)
• All source files have up-to-date hashes in the *.signatures.json files
• sudo make go-tidy-all and sudo make go-test-coverage pass
• Documentation has been updated to match any changes to the build system
• Ready to merge

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Summary

Occasionally we get hit by build failures even though the build summary indicates that all packages built without issues and no specific details to the reason why the build failed are displayed. These failures seem to be random and hard to reproduce.

This change adds additional logging to be printed for such cases to help identify any dangling, unresolved nodes in the build graph, which may help us debug this issue.

Sample outputs:

• Printing all nodes, even duplicates.
  

• Skipping duplicates.
  

Does this affect the toolchain?

No.

Associated issues

• ADO bug.

Test Methodology

• Local builds.
• PR checks running the new unit tests.

[mfrw]

Can we please add some documentation on how to use this :)

[Copilot]

Pull Request Overview

This PR extends the build failure logging to help diagnose sporadic build failures by printing hidden build blockers and refactoring unresolved dependency computations.

• Added a new function PrintHiddenBuildBlockers in printresults.go to log potentially hidden blockers when no obvious failures are present.
• Refactored the unresolved dependencies computation by extracting a new helper getUnresolvedDependencies.
• Updated the fatal error message in scheduler.go to include the build log file for augmented troubleshooting.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
toolkit/tools/scheduler/schedulerutils/printresults.go	Added logging of hidden build blockers and refactored unresolved dependencies handling.
toolkit/tools/scheduler/schedulerutils/depsolver.go	Added a helper to build a subgraph of blocked nodes to support the new logging.
toolkit/tools/scheduler/scheduler.go	Updated fatal error messaging and added call to PrintHiddenBuildBlockers.
toolkit/tools/internal/pkggraph/pkggraph_test.go	Extended test coverage for new unresolved nodes functionality.
toolkit/tools/internal/pkggraph/pkggraph.go	Added AllUnresolvedNodes helper function.
toolkit/tools/internal/pkggraph/graphprinter*.go	New and updated files for graph printing functionality.

Comments suppressed due to low confidence (2)

toolkit/tools/scheduler/schedulerutils/printresults.go:162

• [nitpick] Consider including the goal node identifier or additional context in this log message to aid in debugging hidden blockers when the build unexpectedly fails.

logger.Log.Errorf("Detected a blocked build despite no obvious failures.")

toolkit/tools/scheduler/scheduler.go:228

• [nitpick] Ensure that the fatal error message format remains consistent with other modules, and verify that the inclusion of the log file provides sufficient context for troubleshooting.

logger.Log.Fatalf("Unable to build package graph.\nFor details see the build summary section above and the build log '%s'.\nError: %s.", *logFlags.LogFile, err)