[C++][CI] Add a test job on s390x

[asfimport]

Reporter: Kouhei Sutou / @kou
Assignee: Kouhei Sutou / @kou

PRs and other links:

• GitHub Pull Request #7131

_{Note: This issue was originally created as ARROW-8743. Please see the migration documentation for further details.}

[asfimport]

Kouhei Sutou / @kou:
Issue resolved by pull request 7131
#7131