Fix the shebang of binaries under embedded/bin on *nix platforms.

Fixes https://github.com/opscode/chef/issues/2379. 

I've taken the last option which is not beautiful but is safe and decreases the code churn in the last minute. Thoughts @lamont-granquist, @schisamo ?
I wonder what's the right dsl method to call rather than `puts` here :smile: ?