[lldb] Fix crash in AccessDeclContextSanity when copying FunctionTemplateDecl inside a record.

Summary:
We currently don't set access specifiers for function template declarations. This seems to be fine
as long as the function template is not declared inside any record in which case Clang asserts
with the following once we try to query it's access:
```
Assertion failed: (Access != AS_none && "Access specifier is AS_none inside a record decl"), function AccessDeclContextSanity,
```

This patch just marks these function template declarations as public to make Clang happy.

Reviewers: shafik, teemperor

Reviewed By: teemperor

Subscribers: JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D71909

Author: Teemperor

lldb/packages/Python/lldbsuite/test/commands/expression/completion-crash2/TestCompletionCrash2.py

@@ -0,0 +1,4 @@
+from lldbsuite.test import lldbinline
+from lldbsuite.test import decorators
+
+lldbinline.MakeInlineTest(__file__, globals(), [])

lldb/packages/Python/lldbsuite/test/commands/expression/completion-crash2/Makefile renamed to lldb/packages/Python/lldbsuite/test/commands/expression/regression-access-function-template-in-record/Makefile

@@ -1547,6 +1547,11 @@ clang::FunctionTemplateDecl *ClangASTContext::CreateFunctionTemplateDecl(
     // TODO: verify which decl context we should put template_param_decls into..
     template_param_decls[i]->setDeclContext(func_decl);
   }
+  // Function templates inside a record need to have an access specifier.
+  // It doesn't matter what access specifier we give the template as LLDB
+  // anyway allows accessing everything inside a record.
+  if (decl_ctx->isRecord())
+    func_tmpl_decl->setAccess(clang::AccessSpecifier::AS_public);
 
   return func_tmpl_decl;
 }