[clang] [X86] Add -fexperimental-new-constant-interpreter test coverage to the FMA/FMA4 constexpr test files (PR #155859)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `clang` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/21935

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LLVM-Unit :: Support/./SupportTests/186/386' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/unittests/Support/./SupportTests-LLVM-Unit-3343402-186-386.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=386 GTEST_SHARD_INDEX=186 /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/unittests/Support/./SupportTests
--

Script:
--
/home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/unittests/Support/./SupportTests --gtest_filter=ProgramEnvTest.TestLockFileExclusive
--
../llvm/llvm/unittests/Support/ProgramTest.cpp:648: Failure
Value of: Finished
  Actual: false
Expected: true


../llvm/llvm/unittests/Support/ProgramTest.cpp:648
Value of: Finished
  Actual: false
Expected: true



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


```

</details>

https://github.com/llvm/llvm-project/pull/155859