tests: retrace: skip the test using divide-by-zero on s390x

As stated in the code, GDB seems to have issues with that particular
crash and will either crash itself or not give the proper stack trace.
Since it's not something that we can feasibly fix right now, let's skip
the test on that particular architecture.

tests/system/test_apport_retrace.py

@@ -197,6 +197,10 @@ def _assert_cache_has_content(
 
 
 @pytest.mark.skipif(not has_internet(), reason="online test")
+@pytest.mark.skipif(
+    impl.get_system_architecture() == "s390x",
+    reason="GDB has issues with divide-by-zero on s390x (LP: #2075204)",
+    )
 def test_retrace_system_sandbox(
     workdir: pathlib.Path, module_cachedir: pathlib.Path, divide_by_zero_crash: str
 ) -> None: