[llvm] [DenseMap] memcpy buckets with trivial copy constructor and destructor. NFC (PR #224193)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> Hi, this breaks build on FreeBSD. We still ship _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR in our base. We would like to resolve this by having libcxx.so.2 in our base. But it is not happen for now.

You can remove L486 `static_assert(densemap::detail::isRelocatableBucket<PairBucket>);` from DenseMapTest.cpp in your patched llvm-project.

https://github.com/llvm/llvm-project/pull/224193