CICD: Introduce check-only for Redox CI

[oech3]

• While we don't have enough contributor to fix cargo build on Redox, we can still keep cargo check for Redox. Closes CI failing for redox build #10918 by keeping minimal check.
• Some tests exist only for checking that *con does not cause build failure. But cargo build only for it is overkill. Do check only since cargo check -p uu_chcon fails on the wrong platform.

We should avoid all red anyway.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cut/bounded-memory. tests/cut/bounded-memory is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/factor/t10. tests/factor/t10 is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/factor/t33. tests/factor/t33 is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/factor/t34. tests/factor/t34 is passing on 'main'. Maybe you have to rebase?
Congrats! The gnu test tests/basenc/bounded-memory is now passing!