formula_auditor: ignore implicit dep for Linux gcc audit

[cho-m]

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Implicit GCC is from running an OS with older system GCC and shouldn't cause audit failure.

[Copilot]

Pull request overview

Updates the Linux-only GCC dependency audit in FormulaAuditor to ignore implicit gcc dependencies (e.g., coming from older system toolchains) so they don’t incorrectly trigger audit failures.

Changes:

• Treat gcc as relevant to the Linux-only audit only when it is a non-implicit dependency.

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[MikeMcQuaid]

Makes sense, thanks!