Initialize the filesystem paths to use
from env. env is a hash-like object (typically ENV) that is queried for ‘GEM_HOME’,
‘GEM_PATH’, and ‘GEM_SPEC_CACHE’
# File lib/rubygems.rb, line 339
def self.paths=(env)
clear_paths
@paths = Gem::PathSupport.new env
Gem::Specification.dirs = @paths.path
end