Remove unnecessary dependencies for assert_rb codegen and test_rbireps

mrbgems/mruby-test/mrbgem.rake

@@ -27,7 +27,7 @@ MRuby::Gem::Specification.new('mruby-test') do |spec|
   mrbtest_objs << assert_lib
 
   file assert_lib => assert_c
-  file assert_c => [build.mrbcfile, assert_rb] do |t|
+  file assert_c => assert_rb do |t|
     open(t.name, 'w') do |f|
       mrbc.run f, assert_rb, 'mrbtest_assert_irep'
     end
@@ -41,7 +41,7 @@ MRuby::Gem::Specification.new('mruby-test') do |spec|
     dep_list = build.gems.tsort_dependencies(g.test_dependencies, gem_table).select(&:generate_functions)
 
     file test_rbobj => g.test_rbireps
-    file g.test_rbireps => [g.test_rbfiles].flatten + [File.join(g.dir, 'mrbgem.rake'), g.build.mrbcfile, "#{MRUBY_ROOT}/tasks/mrbgem_spec.rake"] do |t|
+    file g.test_rbireps => [g.test_rbfiles].flatten do |t|
       FileUtils.mkdir_p File.dirname(t.name)
       open(t.name, 'w') do |f|
         g.print_gem_test_header(f)