Do not require a Context to extract the FunctionIndex from Bitcode (NFC)

The LLVMContext was only used for Diagnostic. Pass a DiagnosticHandler
instead.

Differential Revision: http://reviews.llvm.org/D14794

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 253540
diff --git a/llvm/tools/llvm-link/llvm-link.cpp b/llvm/tools/llvm-link/llvm-link.cpp
index 8d0ce0a..c539f75 100644
--- a/llvm/tools/llvm-link/llvm-link.cpp
+++ b/llvm/tools/llvm-link/llvm-link.cpp
@@ -148,7 +148,7 @@
     return EC;
   MemoryBufferRef BufferRef = (FileOrErr.get())->getMemBufferRef();
   ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr =
-      object::FunctionIndexObjectFile::create(BufferRef, Context,
+      object::FunctionIndexObjectFile::create(BufferRef, diagnosticHandler,
                                               ExportingModule);
   EC = ObjOrErr.getError();
   if (EC)