Create unit tests for compiler warning feature behavior

[nradakovic]

What

Provide a lightweight verification suite that catches basic regressions in warning feature wiring and language-specific flag application.

Acceptance Criteria (DoD)

• A unit test setup exists for compiler warning features.
• Tests cover the main warning feature groups.
• Tests cover at least one C compilation path and one C++ compilation path.
• Tests are able to detect incorrect feature wiring or incorrect language-specific flag application.
• The test scope remains intentionally small and focused on migration safety.

How

• Add tests that exercise the supported warning feature groups.
• Verify that the expected warning flags are applied when the corresponding features are enabled.
• Verify that C-only flags are not applied to C++ compilation and that C++-only flags are not applied to C compilation.
• Keep the test setup simple and maintainable, but broad enough to validate the basic behavior of the feature model.