chore: add spec:valgrind task

Author: yoshoku

rumale-tree/Rakefile

@@ -3,7 +3,15 @@
 require 'bundler/gem_tasks'
 require 'rspec/core/rake_task'
 
-RSpec::Core::RakeTask.new(:spec)
+RSpec::Core::RakeTask.new(spec: :compile)
+if ENV['BUNDLE_WITH'] == 'memcheck'
+  require 'ruby_memcheck'
+  require 'ruby_memcheck/rspec/rake_task'
+
+  namespace :spec do
+    RubyMemcheck::RSpec::RakeTask.new(valgrind: :compile)
+  end
+end
 
 require 'rubocop/rake_task'