[clang] [llvm] [HLSL][RootSignature] Update `setDefaultFlags` to account for Root Signature Version (PR #145828)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lldb-remote-linux-win` running on `as-builder-10` while building `clang,llvm` at step 16 "test-check-lldb-unit".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/197/builds/6659

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

```
Step 16 (test-check-lldb-unit) failure: Test just built components: check-lldb-unit completed (failure)
******************** TEST 'lldb-unit :: Host/./HostTests.exe/31/87' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:C:\buildbot\as-builder-10\lldb-x-aarch64\build\tools\lldb\unittests\Host\.\HostTests.exe-lldb-unit-9424-31-87.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=87 GTEST_SHARD_INDEX=31 C:\buildbot\as-builder-10\lldb-x-aarch64\build\tools\lldb\unittests\Host\.\HostTests.exe
--

Script:
--
C:\buildbot\as-builder-10\lldb-x-aarch64\build\tools\lldb\unittests\Host\.\HostTests.exe --gtest_filter=MainLoopTest.NoSpuriousPipeReads
--
C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\lldb\unittests\Host\MainLoopTest.cpp(141): error: Expected equality of these values:
  1u
    Which is: 1
  callback_count
    Which is: 2


C:\buildbot\as-builder-10\lldb-x-aarch64\llvm-project\lldb\unittests\Host\MainLoopTest.cpp:141
Expected equality of these values:
  1u
    Which is: 1
  callback_count
    Which is: 2



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


```

</details>

https://github.com/llvm/llvm-project/pull/145828