Forward #pragma comment(lib/linker) through as flags metadata

Summary:
Most of this change is wiring the pragma all the way through from the
lexer, parser, and sema to codegen.  I considered adding a Decl AST node
for this, but it seemed too heavyweight.

Mach-O already uses a metadata flag called "Linker Options" to do this
kind of auto-linking.  This change follows that pattern.

LLVM knows how to forward the "Linker Options" metadata into the COFF
.drectve section where these flags belong.  ELF support is not
implemented, but possible.

This is related to auto-linking, which is http://llvm.org/PR13016.

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D723

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181426 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/ModuleBuilder.cpp b/lib/CodeGen/ModuleBuilder.cpp
index 69e5b32..56067a4 100644
--- a/lib/CodeGen/ModuleBuilder.cpp
+++ b/lib/CodeGen/ModuleBuilder.cpp
@@ -20,6 +20,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Frontend/CodeGenOptions.h"
 #include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
@@ -115,6 +116,14 @@
 
       Builder->EmitVTable(RD, DefinitionRequired);
     }
+
+    virtual void HandleLinkerOptionPragma(llvm::StringRef Opts) {
+      Builder->AppendLinkerOptions(Opts);
+    }
+
+    virtual void HandleDependentLibrary(llvm::StringRef Lib) {
+      Builder->AddDependentLib(Lib);
+    }
   };
 }