[lld-macho] Refactor parseSections to avoid creating isec on LLVM segments

[thevinster]

Summary

Address post follow up comment in D108016. Avoid creating isec for
LLVM segments since we are skipping over it.

[int3]

Thanks!

[thevinster]

Lint

lld/MachO/InputFiles.cpp

if (sectionType(sec.flags) == S_CSTRING_LITERALS ||
       uint64_t literalSize = target->wordSize == 8 ? 32 : 16;
       subsections.push_back({});
       SubsectionMap &subsecMap = subsections.back();
       for (uint64_t off = 0; off < data.size(); off += literalSize)
         subsecMap.push_back(
             {off, make<ConcatInputSection>(segname, name, this,
                                            data.slice(off, literalSize), align,
                                            flags)});
+    } else if (segname == segment_names::llvm) {
+      // ld64 does not appear to emit contents from sections within the __LLVM
+      // segment. Symbols within those sections point to bitcode metadata
+      // instead of actual symbols. Global symbols within those sections could
+      // have the same name without causing duplicate symbol errors. Push an
+      // empty map to ensure indices line up for the remaining sections.
+      // TODO: Evaluate whether the bitcode metadata is needed.
+      subsections.push_back({});
     } else {
       auto *isec =
           make<ConcatInputSection>(segname, name, this, data, align, flags);
       if (isDebugSection(isec->getFlags()) &&
           isec->getSegName() == segment_names::dwarf) {
         // Instead of emitting DWARF sections, we emit STABS symbols to the
         // object files that contain them. We filter them out early to avoid
         // parsing their relocations unnecessarily. But we must still push an
         // empty map to ensure the indices line up for the remaining sections.
         subsections.push_back({});
         debugSections.push_back(isec);
-      } else if (isec->getSegName() == segment_names::llvm) {
-        // ld64 does not appear to emit contents from sections within the __LLVM
-        // segment. Symbols within those sections point to bitcode metadata
-        // instead of actual symbols. Global symbols within those sections could
-        // have the same name without causing duplicate symbol errors. Push an
-        // empty map to ensure indices line up for the remaining sections.
-        // TODO: Evaluate whether the bitcode metadata is needed.
-        subsections.push_back({});
       } else {
         subsections.push_back({{0, isec}});
       }
     }
   }
 }
 
 // Find the subsection corresponding to the greatest section offset that is <=