[NFC] Fix build failure with GCC 11 in C++20 mode

This was already fixed in
https://github.com/llvm/llvm-project/commit/2ccf0b76bcaf0895e04f14e3ff53c59dd96f9f0f
but then regressed in
https://github.com/llvm/llvm-project/commit/79a1f3e7c6d338b953b4dfe8cd7cb13ba60fe4e7

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D123589