[libcxx-commits] [libcxx] Reapply "[libc++] Avoid constructing additional objects when using map::at" (#160738) (PR #161485)

[Nico Weber via libcxx-commits]

nico wrote:

(If I copy in `CheckStdCmpRequirements` from https://github.com/llvm/llvm-project/pull/160804/files#diff-a3bef0ea0ba4634c49740d0ac2fc8ea0ffa86a65f505c08268415783fea735f6R38-R39 and add `static_assert(CheckStdCmpRequirements<std::less<::Paper>>(), "foo");`, that does pass)

https://github.com/llvm/llvm-project/pull/161485