lld/mach-o should set MH_NO_REEXPORTED_DYLIBS if there are no REEXPORT_DYLIB libraries

[carlokok]

Summary

Currently it doesn't ever set that, this patch sets it unless there are reexported libraries. When this happens ld64 doesn't like linking to it, failing with the error that MH_NO_REEXPORTED_DYLIBS should have been set.

(Thanks to @LemonBoy for helping me with this patch)

[carlokok]

Remove unused var

lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp

   normFile.pageSize = context.pageSize();
   normFile.rpaths = context.rpaths();
   util.addDependentDylibs(atomFile, normFile);
+  if (context.outputMachOType() == MH_DYLIB) {
+     // If we're not re-exporting any dylib set MH_NO_REEXPORTED_DYLIBS
+    normFile.flags = normFile.flags | MH_NO_REEXPORTED_DYLIBS;
+    for (DependentDylib &sect : normFile.dependentDylibs) {
+      if (sect.kind == llvm::MachO::LC_REEXPORT_DYLIB) {
+        normFile.flags = normFile.flags &~ MH_NO_REEXPORTED_DYLIBS;
+        break;
+      }
+    }
+  }
+  
   util.copySegmentInfo(normFile);
   util.copySectionInfo(normFile);
   util.assignAddressesToSections(normFile);