[llvm] Prevent GlobalOpt from folding away addrspacecasts which may be runtime operations. (PR #153753)

[Owen Anderson via llvm-commits]

resistor wrote:

Tagging @davidchisnall as the author of the original change, and @jrtc27 and @arichardson for a CHERI-related change.

https://github.com/llvm/llvm-project/pull/153753