[clang] [Clang][Sema] placement new initializes typedef array with correct size (PR #83124)

[Nico Weber via cfe-commits]

nico wrote:

Looks like this breaks check-clang on mac: http://45.33.8.238/macm1/83529/step_6.txt

Please take a look and revert for now if it takes a while to fix.

https://github.com/llvm/llvm-project/pull/83124