1 files changed, 5 insertions, 1 deletions
diff --git a/tasks/libmruby.rake b/tasks/libmruby.rake
index 887cc69aa..095bedd52 100644
--- a/tasks/libmruby.rake
+++ b/tasks/libmruby.rake
@@ -1,7 +1,10 @@
 MRuby.each_target do
   file libfile("#{build_dir}/lib/libmruby") => libmruby.flatten do |t|
     archiver.run t.name, t.prerequisites
-    open("#{build_dir}/lib/libmruby.flags.mak", 'w') do |f|
+  end
+
+  file "#{build_dir}/lib/libmruby.flags.mak" => [__FILE__, libfile("#{build_dir}/lib/libmruby")] do |t|
+    open(t.name, 'w') do |f|
       f.puts "MRUBY_CFLAGS = #{cc.all_flags.gsub('"', '\\"')}"
 
       gem_flags = gems.map { |g| g.linker.flags }
@@ -15,4 +18,5 @@ MRuby.each_target do
       f.puts "MRUBY_LIBS = #{linker.option_library % 'mruby'} #{linker.library_flags(gem_libraries).gsub('"', '\\"')}"
     end
   end
+  task :all => "#{build_dir}/lib/libmruby.flags.mak"
 end