[SystemZ][z/OS] GOFFObjectFile fix for windows build

[yusra.syeda]

Summary

This patch adds the return of an error code at the end of the getSymbolType function to fix the build error on windows.

[NathanielMcVicar]

Thanks for taking care of this!

[yusra.syeda]

This commit landed and fixes the build error: 14390ecb75b28cca2b151c70bb1718b36876f977. Will close this patch.

llvm/lib/Object/GOFFObjectFile.cpp

case GOFF::ESD_ST_ExternalReference:
     case GOFF::ESD_EXE_CODE:
       return SymbolRef::ST_Function;
     case GOFF::ESD_EXE_DATA:
       return SymbolRef::ST_Data;
     case GOFF::ESD_EXE_Unspecified:
       return SymbolRef::ST_Unknown;
     }
   }
+  return createStringError(llvm::errc::invalid_argument,
+                           "Invalid argument provided");
 }
 
 Expected<section_iterator>
 GOFFObjectFile::getSymbolSection(DataRefImpl Symb) const {
   DataRefImpl Sec;
 
   if (isSymbolUnresolved(Symb))
     return section_iterator(SectionRef(Sec, this));