No need to monkeypatch rubygems, actually

bundler/lib/bundler/dsl.rb

@@ -63,7 +63,7 @@ def gemspec(opts = nil)
       development_group = opts[:development_group] || :development
       expanded_path     = gemfile_root.join(path)
 
-      gemspecs = Gem::Util.glob_files_in_dir("{,*}.gemspec", expanded_path).map {|g| Bundler.load_gemspec(g) }.compact
+      gemspecs = Bundler::SharedHelpers.glob_files_in_dir("{,*}.gemspec", expanded_path).map {|g| Bundler.load_gemspec(g) }.compact
       gemspecs.reject! {|s| s.name != name } if name
       Index.sort_specs(gemspecs)
       specs_by_name_and_version = gemspecs.group_by {|s| [s.name, s.version] }

bundler/lib/bundler/gem_helper.rb

@@ -32,7 +32,7 @@ def gemspec(&block)
 
     def initialize(base = nil, name = nil)
       @base = File.expand_path(base || SharedHelpers.pwd)
-      gemspecs = name ? [File.join(@base, "#{name}.gemspec")] : Gem::Util.glob_files_in_dir("{,*}.gemspec", @base)
+      gemspecs = name ? [File.join(@base, "#{name}.gemspec")] : SharedHelpers.glob_files_in_dir("{,*}.gemspec", @base)
       raise "Unable to determine name from existing gemspec. Use :name => 'gemname' in #install_tasks to manually set it." unless gemspecs.size == 1
       @spec_path = gemspecs.first
       @gemspec = Bundler.load_gemspec(@spec_path)
@@ -111,7 +111,7 @@ def rubygem_push(path)
     end
 
     def built_gem_path
-      Gem::Util.glob_files_in_dir("#{name}-*.gem", base).sort_by {|f| File.mtime(f) }.last
+      SharedHelpers.glob_files_in_dir("#{name}-*.gem", base).sort_by {|f| File.mtime(f) }.last
     end
 
     def git_push(remote = nil)

bundler/lib/bundler/rubygems_ext.rb

@@ -173,22 +173,6 @@ def hash
     undef_method :eql? if method_defined? :eql?
     alias_method :eql?, :==
   end
-
-  require "rubygems/util"
-
-  Util.singleton_class.module_eval do
-    if Util.singleton_methods.include?(:glob_files_in_dir) # since 3.0.0.beta.2
-      remove_method :glob_files_in_dir
-    end
-
-    def glob_files_in_dir(glob, base_path)
-      if RUBY_VERSION >= "2.5"
-        Dir.glob(glob, :base => base_path).map! {|f| File.expand_path(f, base_path) }
-      else
-        Dir.glob(File.join(base_path.to_s.gsub(/[\[\]]/, '\\\\\\&'), glob)).map! {|f| File.expand_path(f) }
-      end
-    end
-  end
 end
 
 module Gem

bundler/lib/bundler/shared_helpers.rb

@@ -205,6 +205,14 @@ def write_to_gemfile(gemfile_path, contents)
       filesystem_access(gemfile_path) {|g| File.open(g, "w") {|file| file.puts contents } }
     end
 
+    def glob_files_in_dir(glob, base_path)
+      if RUBY_VERSION >= "2.5"
+        Dir.glob(glob, :base => base_path).map! {|f| File.expand_path(f, base_path) }
+      else
+        Dir.glob(File.join(base_path.to_s.gsub(/[\[\]]/, '\\\\\\&'), glob)).map! {|f| File.expand_path(f) }
+      end
+    end
+
     private
 
     def validate_bundle_path

bundler/lib/bundler/source/path.rb

@@ -171,7 +171,7 @@ def load_spec_files
 
         if File.directory?(expanded_path)
           # We sort depth-first since `<<` will override the earlier-found specs
-          Gem::Util.glob_files_in_dir(@glob, expanded_path).sort_by {|p| -p.split(File::SEPARATOR).size }.each do |file|
+          SharedHelpers.glob_files_in_dir(@glob, expanded_path).sort_by {|p| -p.split(File::SEPARATOR).size }.each do |file|
             next unless spec = load_gemspec(file)
             spec.source = self