[libcxx-commits] [libcxx] [libc++] Move libcxx/test/libcxx/extensions to libcxx/test/extensions and update the tests (PR #145476)

[Louis Dionne via libcxx-commits]

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

LGTM, but as discussed let's add a `lit.local.cfg` file that marks these tests as requiring libc++ or libstdc++.

As discussed just now, the underlying intent is that other implementations shouldn't have to know about the directory structure of our test suite in order to run our test suite.

https://github.com/llvm/llvm-project/pull/145476