[clang] [Clang] [Parser] Fixing all callers of `ParseExternalDeclaration` that didn't parse gnu attributes (PR #117148)

[Mathys Gasnier via cfe-commits]

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@@ -2314,10 +2314,12 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirectiveWithExtDecl(
       // Here we expect to see some function declaration.
       if (AS == AS_none) {
         assert(TagType == DeclSpec::TST_unspecified);
-        ParsedAttributes EmptyDeclSpecAttrs(AttrFactory);
-        MaybeParseCXX11Attributes(Attrs);
+        ParsedAttributes DeclSpecAttrs(AttrFactory);
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Mathys-Gasnier wrote:

Because `Attrs` is not a local variable but an argument passed to `ParseOpenMPDeclarativeDirectiveWithExtDecl`

https://github.com/llvm/llvm-project/pull/117148