__test_has_construct.
In C++17 some tests started failing after a521532aa1. This fixes those errors by suppressing the deprecation warning when calling `construct` in `__test_has_construct`. This is the same solution as `__has_destroy_test` already uses.
Reviewers: ldionne, #libc!
Subscribers: dexonsmith, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D80481