build: fix require and autoload by adding /lib to $LOAD_PATH

Author: Trim

board-linuxfr.gemspec

@@ -1,4 +1,6 @@
 # encoding: utf-8
+lib = File.expand_path('../lib', __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require './lib/board-linuxfr'
 
 Gem::Specification.new do |s|