Fix reshim behavior on gem uninstall and bundle install.

rubygems-plugin/rubygems_plugin.rb

-# Yes borrowed from rbenv. Couldn't take my mind off that implementation
-
-Gem.post_install do |installer|
-
-  if installer.spec.executables.any? && installer.bin_dir == Gem.default_bindir
-    installer.spec.executables.each do |executable|
-     `asdf reshim ruby #{RUBY_VERSION} bin/#{executable}`
-    end
+module ReshimInstaller
+  def install(options)
+    super
+    # We don't know which gems were installed, so always reshim.
+    `asdf reshim ruby`
   end
+end
 
+if defined?(Bundler::Installer)
+  Bundler::Installer.prepend ReshimInstaller
+else
+  maybe_reshim = lambda do |installer|
+    # If any gems with executables were installed or uninstalled, reshim.
+    `asdf reshim ruby` if installer.spec.executables.any?
+  end
+  Gem.post_install &maybe_reshim
+  Gem.post_uninstall &maybe_reshim
 end