[llvm-install-name-tool] Implement delete_rpath option

This diff adds support for deleting an rpath from a Mach-O binary.

Patch by Sameer Arora!

Test plan: make check-all

Differential revision: https://reviews.llvm.org/D81527
diff --git a/llvm/tools/llvm-objcopy/MachO/Object.h b/llvm/tools/llvm-objcopy/MachO/Object.h
index 5da31d2..e825d18 100644
--- a/llvm/tools/llvm-objcopy/MachO/Object.h
+++ b/llvm/tools/llvm-objcopy/MachO/Object.h
@@ -326,6 +326,11 @@
 
   Error
   removeSections(function_ref<bool(const std::unique_ptr<Section> &)> ToRemove);
+
+  Error removeLoadCommands(function_ref<bool(const LoadCommand &)> ToRemove);
+
+  void updateLoadCommandIndexes();
+
   void addLoadCommand(LoadCommand LC);
 
   /// Creates a new segment load command in the object and returns a reference