[clang] [HLSL] Add StructuredBuffer to external sema source (PR #106316)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-win` running on `sie-win-worker` while building `clang` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/46/builds/4768

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: AST/HLSL/StructuredBuffer-AST.hlsl' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
z:\b\llvm-clang-x86_64-sie-win\build\bin\clang.exe -cc1 -internal-isystem Z:\b\llvm-clang-x86_64-sie-win\build\lib\clang\20\include -nostdsysteminc -triple dxil-pc-shadermodel6.0-library -x hlsl -ast-dump -DEMPTY Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl | z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe -check-prefix=EMPTY Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\clang.exe' -cc1 -internal-isystem 'Z:\b\llvm-clang-x86_64-sie-win\build\lib\clang\20\include' -nostdsysteminc -triple dxil-pc-shadermodel6.0-library -x hlsl -ast-dump -DEMPTY 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl'
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe' -check-prefix=EMPTY 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl'
# RUN: at line 2
z:\b\llvm-clang-x86_64-sie-win\build\bin\clang.exe -cc1 -internal-isystem Z:\b\llvm-clang-x86_64-sie-win\build\lib\clang\20\include -nostdsysteminc -triple dxil-pc-shadermodel6.0-library -x hlsl -ast-dump Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl | z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\clang.exe' -cc1 -internal-isystem 'Z:\b\llvm-clang-x86_64-sie-win\build\lib\clang\20\include' -nostdsysteminc -triple dxil-pc-shadermodel6.0-library -x hlsl -ast-dump 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl'
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe' 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl'
# .---command stderr------------
# | Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl:33:16: error: CHECK-NEXT: expected string not found in input
# | // CHECK-NEXT: FieldDecl 0x{{[0-9A-Fa-f]+}} <<invalid sloc>> <invalid sloc> implicit h 'element_type *'
# |                ^
# | <stdin>:33:62: note: scanning from here
# | | | |-FinalAttr 0x1e700412848 <<invalid sloc>> Implicit final
# |                                                              ^
# | <stdin>:34:5: note: possible intended match here
# | | | |-FieldDecl 0x1e7004223d8 <<invalid sloc>> <invalid sloc> implicit h 'element_type * [[hlsl::resource_class(UAV)]]':'element_type *'
# |     ^
# | 
# | Input file: <stdin>
# | Check file: Z:\b\llvm-clang-x86_64-sie-win\llvm-project\clang\test\AST\HLSL\StructuredBuffer-AST.hlsl
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |            1: TranslationUnitDecl 0x1e700154310 <<invalid sloc>> <invalid sloc> 
# |            2: |-NamespaceDecl 0x1e700154c38 <<invalid sloc>> <invalid sloc> implicit hlsl 
# |            3: | |-TypeAliasTemplateDecl 0x1e700154fa0 <<invalid sloc>> <invalid sloc> implicit vector 
# |            4: | | |-TemplateTypeParmDecl 0x1e700154cc0 <<invalid sloc>> <invalid sloc> class depth 0 index 0 element 
# |            5: | | | `-TemplateArgument type 'float' 
# |            6: | | | `-BuiltinType 0x1e700154520 'float' 
# |            7: | | |-NonTypeTemplateParmDecl 0x1e700154dc0 <<invalid sloc>> <invalid sloc> 'int' depth 0 index 1 element_count 
# |            8: | | | `-TemplateArgument expr '4' 
# |            9: | | | `-IntegerLiteral 0x1e700154e20 <<invalid sloc>> 'int' 4 
# |           10: | | `-TypeAliasDecl 0x1e700154f40 <<invalid sloc>> <invalid sloc> implicit vector 'vector<element, element_count>' 
# |           11: | | `-DependentSizedExtVectorType 0x1e700154ef0 'vector<element, element_count>' dependent <invalid sloc> 
# |           12: | | |-TemplateTypeParmType 0x1e700154d40 'element' dependent depth 0 index 0 
# |           13: | | | `-TemplateTypeParm 0x1e700154cc0 'element' 
# |           14: | | `-DeclRefExpr 0x1e700154e88 <<invalid sloc>> 'int' lvalue NonTypeTemplateParm 0x1e700154dc0 'element_count' 'int' 
# |           15: | |-ClassTemplateDecl 0x1e700155198 <<invalid sloc>> <invalid sloc> implicit RWBuffer 
# |           16: | | |-TemplateTypeParmDecl 0x1e7001550f8 <<invalid sloc>> <invalid sloc> class depth 0 index 0 element_type 
# |           17: | | `-CXXRecordDecl 0x1e700154ff8 <<invalid sloc>> <invalid sloc> implicit <undeserialized declarations> class RWBuffer 
# |           18: | | `-FinalAttr 0x1e7001550a0 <<invalid sloc>> Implicit final 
# |           19: | |-ClassTemplateDecl 0x1e700412568 <<invalid sloc>> <invalid sloc> implicit RasterizerOrderedBuffer 
...

```

</details>

https://github.com/llvm/llvm-project/pull/106316