Remove implicit system crypto forcing on s390x

[surenderky]

PR #220 added a cpu=s390x arm to crypto_system so s390x builds automatically use the system crypto library, since BoringSSL doesn't build on s390x.

Because the arm keys on CPU it forces the -lcrypto path on s390x before any explicit crypto selection is considered, so a consumer that redirects the default crypto dependency can't opt out.

Several CI jobs already select system crypto explicitly with --define=crypto=system the s390x job was the only one relying on the implicit cpu arm. This removes the arm and updates the s390x job to pass --define=crypto=system, making crypto selection explicit and consistent across the matrix.

Fixes Issue #566

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[leonm1]

Hey @surenderky, thank you for the detailed issue report and PR. I can't legally look at the code until you sign the CLA -- can you take a look at the failing gh actions cla/google check?

[surenderky]

Hey @surenderky, thank you for the detailed issue report and PR. I can't legally look at the code until you sign the CLA -- can you take a look at the failing gh actions cla/google check?

Hi @leonm1 the CLA authorization is in process and currently pending with our CLA managers, should be done by today.

[surenderky]

Hi @leonm1 , I have got the CLA authorisation done. could you please review now?

[PiotrSikora]

@surenderky this only changes the default crypto option on s390x back to BoringSSL, which as you noted doesn't work on s390x, so the only thing it does is breaking builds without explicit crypto=system selection.

@leonm1 / @mpwarres could you fix the Zizmor, whatever it is?