[clang] [clang-repl] Fix RuntimeInterfaceBuilder for 32-bit systems (PR #97071)

[Eymen Ünay via cfe-commits]

eymay wrote:

Great work, I can imagine how hard it would be to uncover it!

Small note: I think you may also want to remove the Arm macro guards that mask the unittest in the same commit, as you did in the previous [PR](https://github.com/llvm/llvm-project/pull/96900/files#diff-9b27f347e7ca15f949d4453d24eeca3a6f841a1f7873c86eb98aa44192faaf15) 

https://github.com/llvm/llvm-project/pull/97071