[libc-commits] [libc] [libc][NFC] Fix GCC volatile warning (PR #78509)

[Nick Desaulniers via libc-commits]

nickdesaulniers wrote:

added by @lntue in d6802581700bd.

Honestly, does this test need to use `volatile` at all?  `volatile` is kind of a broken qualifier at least in regards to storage; it should only be used to force loads/stores to be atomic and non-coalesced (by casting the address of an lvalue to a pointer of that type plus volatile, then deferencing that).

https://github.com/llvm/llvm-project/pull/78509