[clang] [clang-repl] Fix the process return code if diagnostics occurred. (PR #89879)

[Vassil Vassilev via cfe-commits]

vgvassilev wrote:

The Unix pre-merge seems okay, however the windows pre-merge check is doing nothing for more than 12h. I will move forward. 

https://github.com/llvm/llvm-project/pull/89879