After read the post in Ruby-China say how to use mechanize and curl to login Ruby-China, I decide to install curb, seems still a little tricky.
First download last available libcurl in windows, which currently is 7.40.0.
Notice most up-to-date version
curl-7.47.1-win32-mingw not working, so still using 7.40.0.
Extract to C:\ and install the curb via below command.
gem install curb --platform=ruby -- --with-curl-lib=C:/curl-7.40.0-devel-mingw32/bin --with-curl-include=C:/curl-7.40.0-devel-mingw32/include
Some relative issues in github about curb, #37, #183
To make SSL certification work, you need to set your windows environment variable, the file can be download here
Finally, need copy all DLL and EXE file in