[libcxx-commits] [libcxx] [libc++][test] extend -linux-gnu XFAIL to cover all of the -linux targets (PR #129140)

[David Spickett via libcxx-commits]

https://github.com/DavidSpickett approved this pull request.

Given that none of these have any details suggesting they pass on non-gnu systems, this seems fine.

Some of them will have been `-gnu` purely because the buildbots at the time were all `-gnu` (probably still are).

https://github.com/llvm/llvm-project/pull/129140