[llvm-objcopy][MachO] Correctly identify object file endianness.

The header magic value is held in the native endianness, so the method used in
cc0ec3f. Use MachOReader / MachOWriter's existing endianness tests instead.

Author: lhames

llvm/tools/llvm-objcopy/MachO/MachOReader.cpp

@@ -206,7 +206,7 @@ void MachOReader::setSymbolInRelocationInfo(Object &O) const {
       for (auto &Reloc : Sec->Relocations)
         if (!Reloc.Scattered)
           Reloc.Symbol = O.SymTable.getSymbolByIndex(
-              Reloc.getPlainRelocationSymbolNum(O.isLittleEndian()));
+              Reloc.getPlainRelocationSymbolNum(MachOObj.isLittleEndian()));
 }
 
 void MachOReader::readRebaseInfo(Object &O) const {

llvm/tools/llvm-objcopy/MachO/MachOWriter.cpp

@@ -242,7 +242,7 @@ void MachOWriter::writeSections() {
         auto RelocInfo = Sec->Relocations[Index];
         if (!RelocInfo.Scattered)
           RelocInfo.setPlainRelocationSymbolNum(RelocInfo.Symbol->Index,
-                                                O.isLittleEndian());
+                                                IsLittleEndian);
 
         if (IsLittleEndian != sys::IsLittleEndianHost)
           MachO::swapStruct(

llvm/tools/llvm-objcopy/MachO/Object.h

@@ -314,11 +314,6 @@ struct Object {
   /// is not too long (SegName.size() should be less than or equal to 16).
   LoadCommand &addSegment(StringRef SegName);
 
-  bool isLittleEndian() const {
-    StringRef Magic(reinterpret_cast<const char *>(&Header.Magic), 4);
-    return Magic == "\xCE\xFA\xED\xFE" || Magic == "\xCF\xFA\xED\xFE";
-  }
-
   bool is64Bit() const {
     return Header.Magic == MachO::MH_MAGIC_64 ||
            Header.Magic == MachO::MH_CIGAM_64;