[llvm-pdbutil] Dump first section contribution for each module.

The DBI stream contains a list of module descriptors.  At the
beginning of each descriptor is a structure representing the first
section contribution in the output file for that module.  LLD
currently doesn't fill out this structure at all, but link.exe
does.  So as a precursor to emitting this data in LLD, we first
need a way to dump it so that it can be checked.

This patch adds support for the dumping, and verifies via a test
that LLD emits bogus information.

llvm-svn: 330208
diff --git a/llvm/lib/DebugInfo/PDB/Native/DbiModuleDescriptor.cpp b/llvm/lib/DebugInfo/PDB/Native/DbiModuleDescriptor.cpp
index dabcc34..931ac7b 100644
--- a/llvm/lib/DebugInfo/PDB/Native/DbiModuleDescriptor.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/DbiModuleDescriptor.cpp
@@ -49,6 +49,10 @@
          ModInfoFlags::TypeServerIndexShift;
 }
 
+const SectionContrib &DbiModuleDescriptor::getSectionContrib() const {
+  return Layout->SC;
+}
+
 uint16_t DbiModuleDescriptor::getModuleStreamIndex() const {
   return Layout->ModDiStream;
 }