[CodeGen] Fix invalid DWARF info on Win64

The relocations for `DIEEntry::EmitValue` were wrong for Win64
(emitting FK_Data_4 instead of FK_SecRel_4). This corrects that
oversight so that the DWARF data is correct in Win64 COFF files.

Fixes PR15393.

Patch by Jameson Nash <jameson@juliacomputing.com> based on a patch
by David Majnemer.

Differential Revision: https://reviews.llvm.org/D21731

llvm-svn: 289013
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index ebbf811..96fb566 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -125,7 +125,7 @@
   if (!IsSectionRelative)
     EmitValueImpl(MCSymbolRefExpr::create(Sym, getContext()), Size);
   else
-    EmitCOFFSecRel32(Sym);
+    EmitCOFFSecRel32(Sym, /*Offset=*/0);
 }
 
 void MCStreamer::EmitDTPRel64Value(const MCExpr *Value) {
@@ -689,8 +689,7 @@
 void MCStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {
 }
 
-void MCStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) {
-}
+void MCStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset) {}
 
 /// EmitRawText - If this file is backed by an assembly streamer, this dumps
 /// the specified string in the output .s file.  This capability is