Checksum clair executable

What does this MR do?

Checksum the binary downloaded during job runtime.

Does this MR meet the acceptance criteria?

Warning: The binary should be stable. If not, the job will just stop working until we update and ship the template. Maybe we should mirror it.

Conformity

• [-] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios. (not user facing)
• [-] Documentation created/updated or follow-up review issue created
• [-] Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Performance and testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Proof of concept: gitlab-org/security-products/tests/webgoat!9 (closed)

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

/cc @gonzoyumo for assignment and awareness (and labels check :))