Restore "Support for ThinLTO function importing and symbol linking."

This restores commit r251837, with the new library dependence added to
llvm-link/Makefile to address bot failures.

llvm-svn: 251866

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -5813,12 +5813,12 @@ llvm::getBitcodeTargetTriple(MemoryBufferRef Buffer, LLVMContext &Context,
 ErrorOr<std::unique_ptr<FunctionInfoIndex>>
 llvm::getFunctionInfoIndex(MemoryBufferRef Buffer, LLVMContext &Context,
                            DiagnosticHandlerFunction DiagnosticHandler,
-                           bool IsLazy) {
+                           const Module *ExportingModule, bool IsLazy) {
   std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
   FunctionIndexBitcodeReader R(Buf.get(), Context, DiagnosticHandler, IsLazy);
 
   std::unique_ptr<FunctionInfoIndex> Index =
-      llvm::make_unique<FunctionInfoIndex>();
+      llvm::make_unique<FunctionInfoIndex>(ExportingModule);
 
   auto cleanupOnError = [&](std::error_code EC) {
     R.releaseBuffer(); // Never take ownership on error.