Add -fmodules-autolink/-fno-modules-autolink (defaults to on) so that
users can explicitly enable/disable modules autolinking.

llvm-svn: 172592
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index b1bdc0f..38f457a 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -173,7 +173,10 @@
   EmitCtorList(GlobalDtors, "llvm.global_dtors");
   EmitGlobalAnnotations();
   EmitLLVMUsed();
-  EmitModuleLinkOptions();
+
+  if (CodeGenOpts.ModulesAutolink) {
+    EmitModuleLinkOptions();
+  }
 
   SimplifyPersonality();