Unable to install RMagick on Windows 8 x64

D:>C:\usr\bin\Ruby193\devkitvars.bat
Adding the DevKit to PATH…

D:>gem install rmagick --platform=ruby –
–with-opt-lib=C:/Progra~1/ImageMagick-6.7.9-Q16/lib
–with-opt-include=C:/Progra~1/ImageMagick-6.7.9-Q16/include
Building native extensions. This could take a while…
Cont.: ERROR: Error installing rmagick: ERROR: Failed to build gem native ext - Pastebin.com

mkmf.log: checking for Ruby version >= 1.8.5... -------------------- yes-------------- - Pastebin.com