[llvm] [SHT_LLVM_BB_ADDR_MAP] Avoids side-effects in addition since order is unspecified. (PR #79168)

[Micah Weston via llvm-commits]

red1bluelost wrote:

I double checked on my Windows machine (VS 2022) with check-llvm. Gonna merge it since the build PR checks are unrelated to BBAddrMap.

https://github.com/llvm/llvm-project/pull/79168