[clang] [llvm] [Clang-Repl] Add support for out-of-process execution. (PR #110418)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-darwin` running on `doug-worker-3` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/23/builds/4728

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: Interpreter/out-of-process.cpp' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
RUN: at line 3: cat /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Interpreter/out-of-process.cpp | /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/clang-repl -oop-executor -orc-runtime | /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/FileCheck /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Interpreter/out-of-process.cpp
+ cat /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Interpreter/out-of-process.cpp
+ /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/clang-repl -oop-executor -orc-runtime
+ /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/FileCheck /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Interpreter/out-of-process.cpp
clang-repl: No such file or directory
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/FileCheck /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Interpreter/out-of-process.cpp

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/110418