[libcxx-commits] [libcxx] [libc++] tests: add long-double-is-double feature (PR #77076)

[Mark de Wever via libcxx-commits]

https://github.com/mordante requested changes to this pull request.

In general we try to avoid feature macros when they are used once.
Since this test planned to be removed I rather keep the status quo. Otherwise we have a test macro with 0 users.

https://github.com/llvm/llvm-project/pull/77076