Fix default gem loading in `generate_gem_table`.

tasks/mrbgem_spec.rake

@@ -298,7 +298,7 @@ module MRuby
         @ary.empty?
       end
 
-      def generate_gem_table
+      def generate_gem_table build
         gem_table = @ary.reduce({}) { |res,v| res[v.name] = v; res }
 
         default_gems = []
@@ -381,7 +381,7 @@ module MRuby
       end
 
       def check(build)
-        gem_table = generate_gem_table
+        gem_table = generate_gem_table build
 
         @ary = tsort_dependencies gem_table.keys, gem_table, true
 

tasks/mrbgems_test.rake

 MRuby.each_target do
-  gem_table = gems.generate_gem_table
+  gem_table = gems.generate_gem_table self
 
   gems.each do |g|
     test_rbobj = g.test_rbireps.ext(exts.object)