The UI tests are written assuming --remap-path-prefix is not used (remap-debuginfo in config.toml). The consequence is that the error messages may include paths and snippets into the standard library. When remap-debuginfo is enabled, these messages change in format and structure because rustc will not show paths and snippets into the standard library.

This normally isn't a problem for the "main" platforms (linux/macos/windows), because the CI infrastructure is set up so that the tests run without remap-debuginfo, but the dist artifacts are built separately with remap-debuginfo enabled. However, some of the lower-tier platforms perform both tests and distribution in a single step with remap-debuginfo enabled. This also affects developers and distributors who use remap-debuginfo.

To sidestep this problem, we add a way to ignore tests in specific platform triples, and update the overly broad ignore-x86 rule in affected tests.

Address #46948, #54546, #53081.