[clang] [clang][SYCL Upstreaming] Add sycl_external attribute and restrict emitting device code (PR #140282)

[Mariya Podchishchaeva via cfe-commits]

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@@ -7179,6 +7179,12 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_EnumExtensibility:
     handleEnumExtensibilityAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_SYCLKernel:
+    S.SYCL().handleKernelAttr(D, AL);
+    break;
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Fznamznon wrote:

I think this is causing the build failures in the CI now.
```suggestion
```

https://github.com/llvm/llvm-project/pull/140282