title: error on bundle install for sassc on cygwin
body: <p>I am using Cygwin to on my windows machine to use RVM and run my rails project. Now when I run bundle install it is showing the following message. </p>
  
  <pre><code>Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
  
      current directory: /home/Shila/.rvm/gems/ruby-2.6.3/gems/sassc-2.2.1/ext
  /home/Shila/.rvm/rubies/ruby-2.6.3/bin/ruby.exe -I /home/Shila/.rvm/rubies/ruby-2.6.3/lib/ruby/site_ruby/2.6.0 -r ./siteconf20200414-4993-go8jx2.rb extconf.rb
  creating Makefile
  
  current directory: /home/Shila/.rvm/gems/ruby-2.6.3/gems/sassc-2.2.1/ext
  make "DESTDIR=" clean
  
  current directory: /home/Shila/.rvm/gems/ruby-2.6.3/gems/sassc-2.2.1/ext
  make "DESTDIR="
  compiling ./libsass/src/ast.cpp
  CC: fatal error: cannot execute ‘cc1plus’: spawn: No such file or directory
  compilation terminated.
  make: *** [Makefile:236: ast.o] Error 1
  
  make failed, exit code 2
  
  Gem files will remain installed in /home/Shila/.rvm/gems/ruby-2.6.3/gems/sassc-2.2.1 for inspection.
  Results logged to /home/Shila/.rvm/gems/ruby-2.6.3/extensions/x86_64-cygwin/2.6.0/sassc-2.2.1/gem_make.out
  
  An error occurred while installing sassc (2.2.1), and Bundler cannot continue.
  Make sure that `gem install sassc -v '2.2.1' --source 'https://rubygems.org/'` succeeds before bundling.
  
  In Gemfile:
    sass-rails was resolved to 6.0.0, which depends on
      sassc-rails was resolved to 2.1.2, which depends on
        sassc
  
  </code></pre>
  
  <p>ruby version is  2.6.3</p>
  
  <p>Bundler version 1.17.3</p>