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

[Erich Keane via cfe-commits]

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@@ -12937,6 +12937,10 @@ bool ASTContext::DeclMustBeEmitted(const Decl *D) {
   if (D->hasAttr<WeakRefAttr>())
     return false;
 
+  if (LangOpts.SYCLIsDevice && !D->hasAttr<SYCLKernelEntryPointAttr>() &&
+      !D->hasAttr<SYCLExternalAttr>())
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erichkeane wrote:

This doesn't seem right to me, as it changes/causes us to miss some of the below, right?

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