Add ObjWriter API to set DWARF version (llvm#161)

Contributes to https://github.com/dotnet/runtimelab/issues/1738.

Author: MichalStrehovsky

llvm/tools/objwriter/objwriter.cpp

@@ -204,6 +204,10 @@ void ObjectWriter::Finish() {
   Streamer->Finish();
 }
 
+void ObjectWriter::SetDwarfVersion(uint16_t v) {
+  Streamer->getContext().setDwarfVersion(v);
+}
+
 void ObjectWriter::SwitchSection(const char *SectionName,
                                  CustomSectionAttributes attributes,
                                  const char *ComdatName) {

llvm/tools/objwriter/objwriter.exports

@@ -1,5 +1,6 @@
 InitObjWriter
 FinishObjWriter
+SetDwarfVersion
 SwitchSection
 SetCodeSectionAttribute
 EmitAlignment

llvm/tools/objwriter/objwriter.h

@@ -70,6 +70,7 @@ class ObjectWriter {
   bool Init(StringRef FunctionName, const char* tripleName = nullptr);
   void Finish();
 
+  void SetDwarfVersion(uint16_t v);
   void SwitchSection(const char *SectionName,
                      CustomSectionAttributes attributes,
                      const char *ComdatName);
@@ -213,6 +214,11 @@ DLL_EXPORT STDMETHODCALLTYPE void FinishObjWriter(ObjectWriter *OW) {
   delete OW;
 }
 
+DLL_EXPORT STDMETHODCALLTYPE void SetDwarfVersion(ObjectWriter *OW, uint16_t v) {
+  assert(OW && "ObjWriter is null");
+  OW->SetDwarfVersion(v);
+}
+
 DLL_EXPORT STDMETHODCALLTYPE void SwitchSection(ObjectWriter *OW, const char *SectionName,
                               CustomSectionAttributes attributes,
                               const char *ComdatName) {