[llvm-objcopy] - Do not drop the OS/ABI and ABIVersion fields of ELF header

This is https://bugs.llvm.org/show_bug.cgi?id=40005,

Patch teaches llvm-objcopy to preserve OS/ABI and ABIVersion fields of ELF header.
(Currently, it drops them to zero).

Differential revision: https://reviews.llvm.org/D55886

llvm-svn: 349738
diff --git a/llvm/tools/llvm-objcopy/ELF/Object.h b/llvm/tools/llvm-objcopy/ELF/Object.h
index 4b84065..4b606c4 100644
--- a/llvm/tools/llvm-objcopy/ELF/Object.h
+++ b/llvm/tools/llvm-objcopy/ELF/Object.h
@@ -733,6 +733,8 @@
   Segment ElfHdrSegment;
   Segment ProgramHdrSegment;
 
+  uint8_t OSABI;
+  uint8_t ABIVersion;
   uint64_t Entry;
   uint64_t SHOffset;
   uint32_t Type;