lld: Don't write preemptible symbol values to the .got.

It is not necessary and matches what bfd and gold do.

This was a regression from [LLVM] r315658.

Obtained from:	LLVM r321023 by Rafael Espíndola

contrib/llvm/tools/lld/ELF/Relocations.cpp

@@ -812,7 +812,7 @@ static void addGotEntry(SymbolBody &Sym, bool Preemptible) {
     //
     // This is ugly -- the difference between REL and RELA should be
     // handled in a better way. It's a TODO.
-    if (!Config->IsRela)
+    if (!Config->IsRela && !Preemptible)
       InX::Got->Relocations.push_back({R_ABS, Target->GotRel, Off, 0, &Sym});
   }
 }