[SASS] 설치 오류 - ffi

공식홈페이지의 방법대로 SASS 설치 시 ffi 관련 에러가 나며 설치가 정상적으로 되지 않았다.

아래와 같이 SASS를 정상적으로 설치할 수 있었다.
(ruby 설치가 되어있는 상황)

C:\Users\1004lucifer\IdeaProjects\Project\gentelella>gem install sass
Fetching: rb-fsevent-0.10.2.gem (100%)
Successfully installed rb-fsevent-0.10.2
Fetching: ffi-1.9.18-x64-mingw32.gem (100%)
ERROR:  Error installing sass:
        The last version of ffi (< 2, >= 0.5.0) to support your Ruby & RubyGems was 1.9.18. Try installing it with `gem install ffi -v 1.9.18` and then running the current command again
        ffi requires Ruby version < 2.5, >= 2.0. The current ruby version is 2.5.0.

C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>gem install ffi -v 1.9.18
ERROR:  Error installing ffi:
        The last version of ffi (= 1.9.18) to support your Ruby & RubyGems was 1.9.18. Try installing it with `gem install ffi -v 1.9.18`
        ffi requires Ruby version < 2.5, >= 2.0. The current ruby version is 2.5.0.

C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>ruby -v
ruby 2.5.0p0 (2017-12-25 revision 61468) [x64-mingw32]

C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>gem install ffi -f
Successfully installed ffi-1.9.18-x64-mingw32
Parsing documentation for ffi-1.9.18-x64-mingw32
Installing ri documentation for ffi-1.9.18-x64-mingw32
Done installing documentation for ffi after 3 seconds
1 gem installed

C:\Users\1004lucifer\IdeaProjects\Project\gentelella>
C:\Users\1004lucifer\IdeaProjects\Project\gentelella>gem install sass
Fetching: rb-inotify-0.9.10.gem (100%)
Successfully installed rb-inotify-0.9.10
Fetching: sass-listen-4.0.0.gem (100%)
Successfully installed sass-listen-4.0.0
Fetching: sass-3.5.5.gem (100%)
Successfully installed sass-3.5.5
Parsing documentation for rb-inotify-0.9.10
Installing ri documentation for rb-inotify-0.9.10
Parsing documentation for sass-listen-4.0.0
Installing ri documentation for sass-listen-4.0.0
Parsing documentation for sass-3.5.5
Installing ri documentation for sass-3.5.5
Done installing documentation for rb-inotify, sass-listen, sass after 21 seconds
3 gems installed

C:\Users\1004lucifer\IdeaProjects\Project\gentelella>