Object: Move datalayout check into irsymtab::build. NFCI.

[pcc]

Summary

This check is a requirement of the irsymtab builder, not of any
particular caller.

[tejohnson]

LGTM

llvm/lib/Object/IRSymtab.cpp

struct Builder {
   Error addSymbol(const ModuleSymbolTable &Msymtab,
                   const SmallPtrSet<GlobalValue *, 8> &Used,
                   ModuleSymbolTable::Symbol Sym);
 
   Error build(ArrayRef<Module *> Mods);
 };
 
 Error Builder::addModule(Module *M) {
+  if (M->getDataLayoutStr().empty())
+    return make_error<StringError>("input module has no datalayout",
+                                   inconvertibleErrorCode());
+
   SmallPtrSet<GlobalValue *, 8> Used;
   collectUsedGlobalVariables(*M, Used, /*CompilerUsed*/ false);
 
   ModuleSymbolTable Msymtab;
   Msymtab.addModule(M);
 
   storage::Module Mod;
   Mod.Begin = Syms.size();
static Expected<FileContents> upgrade(ArrayRef<BitcodeModule> BMs) {
   std::vector<std::unique_ptr<Module>> OwnedMods;
   for (auto BM : BMs) {
     Expected<std::unique_ptr<Module>> MOrErr =
         BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true,
                          /*IsImporting*/ false);
     if (!MOrErr)
       return MOrErr.takeError();
 
-    if ((*MOrErr)->getDataLayoutStr().empty())
-      return make_error<StringError>("input module has no datalayout",
-                                     inconvertibleErrorCode());
-
     Mods.push_back(MOrErr->get());
     OwnedMods.push_back(std::move(*MOrErr));
   }
 
   if (Error E = build(Mods, FC.Symtab, FC.Strtab))
     return std::move(E);
 
   FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()},