mkmf.rb: adjust default library path
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39371 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
mkmf.rb: adjust default library path
for multiarch. [Bug #7874]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39371 b2dd03c8-39d4-4d8f-98ff-823fe69b080e