I want to set LC_ALL => nil for 1.9/2.0 -- if LC_ALL in chef-client is set to jp_JP.SJIS or whatever, I want to pass that LC_ALL through mixlib-shellout to diff -u 

setting LC_ALL => 'C' on 1.8 is redundant with mixlib-shellout, but it means i don't have to special case passing the :env to mixlib-shellout or not, and can just rely on the ternary operator...