Fix deletion of duplicate rpaths (#357)

* Fix deletion of duplicate rpaths

Deferring field population to the end seems to break rpath deletion of
duplicated rpaths.

Closes #356.

* Add test for deleting duplicate rpaths

lib/macho/macho_file.rb

@@ -418,11 +418,8 @@ def delete_rpath(path, _options = {})
       rpath_cmds = command(:LC_RPATH).select { |r| r.path.to_s == path }
       raise RpathUnknownError, path if rpath_cmds.empty?
 
-      # delete the commands in reverse order, offset descending. this
-      # allows us to defer (expensive) field population until the very end
-      rpath_cmds.reverse_each { |cmd| delete_command(cmd, :repopulate => false) }
-
-      populate_fields
+      # delete the commands in reverse order, offset descending.
+      rpath_cmds.reverse_each { |cmd| delete_command(cmd) }
     end
 
     # Write all Mach-O data to the given filename.

test/test_macho.rb

@@ -443,6 +443,10 @@ def test_delete_rpath
       end
     end
 
+    groups << ["libdupe.dylib", "libdupe_actual.dylib"].map do |fn|
+      fixture(:x86_64, fn)
+    end
+
     groups.each do |filename, actual|
       file = MachO::MachOFile.new(filename)
 
@@ -460,6 +464,7 @@ def test_delete_rpath
       # ensure we can actually re-load and parse the modified file
       modified = MachO::MachOFile.new(actual)
 
+      assert_empty modified.rpaths
       assert_equal file.serialize.bytesize, modified.serialize.bytesize
       assert_operator modified.ncmds, :<, orig_ncmds
       assert_operator modified.sizeofcmds, :<, orig_sizeofcmds