feat: restore debug build for c part of oneDAL

[Alexandr-Solovev]

Description

Summary

Strengthens the ABI check job in two ways:

1. Build host libraries with debug symbols so abidiff can use DWARF and perform full function/variable sub-type diffs (previously it only saw stripped ELF symbols and degraded to add/remove detection on every library).
2. Add a cross-flavor public-symbol drift check to abi_check.sh that compares the set of newly-exported symbols between the host (_c) and DPC++ flavors of each library and hard-fails when they diverge.

Changes

.github/workflows/ci.yml

• Make daal and Make onedal (target oneapi_c) now pass --debug symbols to build.sh, so libonedal_core.so, libonedal.so, libonedal_thread.so, and libonedal_parameters.so ship DWARF into the ABI job.
• oneapi_dpc intentionally stays without debug symbols — DPC++ device DWARF blows up per-object size and icx peak RSS at -j20 and OOMs the runner. A TODO comment documents follow-ups (-Xarch_device -g0 / -fsycl-device-debug=none / larger runner) for enabling it later.
• The "Check ABI conformance" step banner now spells out which libraries were built with debug info and which fall back to symbol add/remove.

.ci/scripts/abi_check.sh

Adds a supplemental block after the existing per-library abidiff loop:

• For each (_c, _dpc) library pair
  (libonedal.so ↔ libonedal_dpc.so, libonedal_parameters.so ↔ libonedal_parameters_dpc.so):
  • Compute the set of newly-exported .dynsym symbols on both sides
    (comm -13 over nm -D --defined-only --extern-only output against __release_lnx_main).
  • Diff the two "new" sets. Any symbol added to one flavor but not the other is reported as ::error:: and increments RETURN_CODE, turning CI red.
• Works on .dynsym alone — no debug info required, so it complements the DWARF-based abidiff pass on the stripped DPC++ libraries.
• libonedal_core.so / libonedal_thread.so skipped (no _dpc counterpart).
• if [ ! -f ] guards make the block a no-op when a flavor is missing.

Rationale

Under the pre-change layout, the DPC++ libraries were built stripped, so abidiff on libonedal_dpc.so silently degraded to symbol-add/remove detection while advertising itself as an ABI check. Any layout change, return-type break, or member-function signature change on a class exported by the DPC++ flavor would pass. The cross-flavor drift check gives us a cheap second line of defense: a PR that adds a public symbol to only one flavor almost always indicates either a missed re-export or an unintentional divergence of the public surface, and a reviewer should look at it either way.

Completeness and readability

• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes or created a separate PR with updates and provided its number in the description, if necessary.
• Git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details).
• I have resolved any merge conflicts that might occur with the base branch.

Testing

• I have run it locally and tested the changes extensively.
• All CI jobs are green or I have provided justification why they aren't.
• I have extended testing suite if new functionality was introduced in this PR.

Performance

• I have measured performance for affected algorithms using scikit-learn_bench and provided at least a summary table with measured data, if performance change is expected.
• I have provided justification why performance and/or quality metrics have changed or why changes are not expected.
• I have extended the benchmarking suite and provided a corresponding scikit-learn_bench PR if new measurable functionality was introduced in this PR.

[Copilot]

Pull request overview

This PR strengthens the Linux ABI conformance job by improving ABI diff fidelity (via DWARF-enabled host builds) and adding an additional guardrail that detects cross-flavor public symbol drift between host (_c) and DPC++ (_dpc) library variants.

Changes:

• Build host-side libraries with REQDBG=symbols (via --debug symbols) so abidiff can use DWARF for deeper ABI comparisons.
• Add a cross-flavor “newly-exported symbols” drift check in .ci/scripts/abi_check.sh to fail CI when host vs DPC++ newly-added public symbols diverge.
• Improve ABI job console messaging to clarify which libraries use DWARF-based checks vs ELF-symbol-only fallback.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/ci.yml	Enables debug-symbol builds for host libraries used by the ABI job and documents why DPC++ remains non-DWARF in CI.
.ci/scripts/abi_check.sh	Adds a cross-flavor symbol drift check after abidiff to detect mismatched newly-exported public symbols.