this class hijacks the functionality of Gem::Installer by overloading its initializer to only provide the information needed by Gem::Installer#build_extensions (which happens to be what we have)

Methods
Public Class methods
new(spec, gem_dir)

Source: show | on GitHub 

    # File railties/lib/rails/gem_builder.rb, line 11
11:     def initialize(spec, gem_dir)
12:       @spec    = spec
13:       @gem_dir = gem_dir
14:     end
Public Instance methods
say(message)

silence the underlying builder

Source: show | on GitHub 

    # File railties/lib/rails/gem_builder.rb, line 17
17:     def say(message)
18:     end