std: Be sure to modify atomics in tests
std: Be sure to modify atomics in tests

See #49775 for some more information but it looks like this is working around an
LLVM bug for the time being.

Closes #49775

GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust