[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 `clang-aarch64-sve-vla-2stage` running on `linaro-g3-04` while building `clang` at step 12 "ninja check 2".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/41/builds/3377

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

```
Step 12 (ninja check 2) failure: stage 2 checked (failure)
******************** TEST 'Clang :: Interpreter/out-of-process.cpp' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
RUN: at line 3: cat /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/clang/test/Interpreter/out-of-process.cpp | /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/bin/clang-repl -oop-executor -orc-runtime | /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/clang/test/Interpreter/out-of-process.cpp
+ cat /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/clang/test/Interpreter/out-of-process.cpp
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/bin/clang-repl -oop-executor -orc-runtime
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/clang/test/Interpreter/out-of-process.cpp
clang-repl: No such file or directory
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/clang/test/Interpreter/out-of-process.cpp

--

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


```

</details>

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