Fix --relocatable on systems that use lib64.
Fix --relocatable on systems that use lib64.

This commit resolves https://github.com/pypa/virtualenv/issues/78.

haridsv/virtualenv,dstufft/virtualenv,vvtam/virtualenv,techtonik/virtualenv,davidszotten/virtualenv,blueyed/virtualenv,jedie/virtualenv,RAS-ViVa/virtualenv,Seha16/virtualenv,Lyleo/virtualenv,mykemunson/virtualenv,Ivoz/virtualenv,haridsv/virtualenv,jedie/virtualenv,francatore/virtualenv,dstufft/virtualenv,ionelmc/virtualenv,madprog/virtualenv,francatore/virtualenv,RAS-ViVa/virtualenv,Ivoz/virtualenv,ionelmc/virtualenv,bigplus/virtualenv,kissthink/virtualenv,mykemunson/virtualenv,Seha16/virtualenv,bigplus/virtualenv,ionelmc/virtualenv,madprog/virtualenv,blueyed/virtualenv,kissthink/virtualenv,techtonik/virtualenv,davidszotten/virtualenv,Lyleo/virtualenv,vvtam/virtualenv