Fix -Wmissing-variable-declarations regression.

This issue was introduced in r181677.

PR17349.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191339 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 92400df..fa51aa4 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -8683,7 +8683,7 @@
   }
 
   if (var->isThisDeclarationADefinition() &&
-      var->isExternallyVisible() &&
+      var->isExternallyVisible() && var->hasLinkage() &&
       getDiagnostics().getDiagnosticLevel(
                        diag::warn_missing_variable_declarations,
                        var->getLocation())) {