[llvm] Run delta-pass with child process (PR #87647)

[Vivek Pandya via llvm-commits]

vivekvpandya wrote:

Just to note for other reviewers we have tested this by setting default value for `--run-delta-in-child` to true. Also we added explicit abort to a delta pass for testing and when such thing happens in child process , parent reports name of that delta pass. 

https://github.com/llvm/llvm-project/pull/87647