PIX: Partial cherry pick of validator version fix (#6908)

Partial cherry pickfrom commit  0fd84aa814

0fd84aa814
Original PR:
https://github.com/microsoft/DirectXShaderCompiler/pull/6901

tools/clang/unittests/HLSL/PixTest.cpp

@@ -526,8 +526,17 @@ void Miss( inout Payload payload )
   TestPixUAVCase(hlsl, L"lib_6_3", L"");
   TestPixUAVCase(hlsl, L"lib_6_4", L"");
   TestPixUAVCase(hlsl, L"lib_6_5", L"");
+
+  if (m_ver.SkipDxilVersion(1, 6))
+    return;
   TestPixUAVCase(hlsl, L"lib_6_6", L"");
+
+  if (m_ver.SkipDxilVersion(1, 7))
+    return;
   TestPixUAVCase(hlsl, L"lib_6_7", L"");
+
+  if (m_ver.SkipDxilVersion(1, 8))
+    return;
   TestPixUAVCase(hlsl, L"lib_6_8", L"");
 }