[ELF] - Give automatically generated __start_* and __stop_* symbols default visibility.

This patch is opposite to D19024, which made this symbols to be hidden by default.

Unfortunately FreeBSD loader wants to see
start_set_modmetadata_set/stop_set_modmetadata_set in the dynamic symbol table. 
They were not placed there because had hidden visibility.

Patch makes them to have default visibility again.

Differential revision: https://reviews.llvm.org/D23552

llvm-svn: 279262
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 6b037a0..9cfbb48 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -51,8 +51,8 @@
 }
 
 template <class ELFT> static void addSynthetic(SymbolAssignment *Cmd) {
-  Symbol *Sym = Symtab<ELFT>::X->addSynthetic(Cmd->Name, nullptr, 0);
-  Sym->Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
+  Symbol *Sym = Symtab<ELFT>::X->addSynthetic(
+      Cmd->Name, nullptr, 0, Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT);
   Cmd->Sym = Sym->body();
 }