[MachO] Add missing byte-swaps when reading dyld_info

[tstellar]

Summary

This fixes the following tests on big-endian hosts:

lld :: mach-o/dylib-install-names.yaml
lld :: mach-o/force_load-dylib.yaml
lld :: mach-o/lib-search-paths.yaml
lld :: mach-o/upward-dylib-load-command.yaml

[ruiu]

LGTM

lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileBinaryReader.cpp

for (unsigned i=0; i < dataInCodeSize/sizeof(data_in_code_entry); ++i) {
           (DataRegionType)read16((const uint8_t *)&dataInCode[i].kind, isBig);
       f->dataInCode.push_back(entry);
     }
   }
 
   if (dyldInfo) {
     // If any exports, extract and add to normalized exportInfo vector.
     if (dyldInfo->export_size) {
-      const uint8_t *trieStart = reinterpret_cast<const uint8_t*>(start +
-                                                          dyldInfo->export_off);
-      ArrayRef<uint8_t> trie(trieStart, dyldInfo->export_size);
+      const uint8_t *trieStart = reinterpret_cast<const uint8_t *>(
+          start + read32(&dyldInfo->export_off, isBig));
+      ArrayRef<uint8_t> trie(trieStart, read32(&dyldInfo->export_size, isBig));
       for (const ExportEntry &trieExport : MachOObjectFile::exports(trie)) {
         Export normExport;
         normExport.name = trieExport.name().copy(f->ownedAllocations);
         normExport.offset = trieExport.address();
         normExport.kind = ExportSymbolKind(trieExport.flags() & EXPORT_SYMBOL_FLAGS_KIND_MASK);
         normExport.flags = trieExport.flags() & ~EXPORT_SYMBOL_FLAGS_KIND_MASK;
         normExport.otherOffset = trieExport.other();
         if (!trieExport.otherName().empty())