[yaml2obj][ELF] Add support for st_value and st_size.

After this patch, the ELF file produced by
`yaml2obj-elf-symbol-basic.yaml`, when linked and executed on x86_64
(under SysV ABI, obviously; I tested on Linux), produces a working
executable that goes into an infinite loop!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184469 91177308-0d34-0410-b5e6-96231b3b80d8

tools/yaml2obj/yaml2elf.cpp

@@ -206,6 +206,8 @@ static void handleSymtabSectionHeader(
       exit(1);
     }
     Symbol.st_shndx = Index;
+    Symbol.st_value = Sym.Value;
+    Symbol.st_size = Sym.Size;
     Syms.push_back(Symbol);
   }