[clang] Compile error for coroutines + new operator

After change https://github.com/llvm/llvm-project/commit/cd67cfecb1a154d0759783ae926f8b44c104d7d3, clang builds error out for use of operator new with coroutines aligned allocations.

Proposed fix with test reproducer: https://github.com/llvm/llvm-project/pull/215619.

Opening issue to track, based on the PR feedback and delay in review.

Per https://llvm.org/docs/DeveloperPolicy.html, path forward here is likely:
"If a test case that demonstrates a problem is reported in the commit thread, please revert and investigate offline.", in order to verify the proposed fix is the right one.