nonguix: Allow disabling passing $0 in make-wrapper.

This small pull request adds a pass-$0? argument to make-wrapper. I'm trying to package something that requires a wrapper, but "exec -a "$0"" makes it fail: it tries to find data relative to its $0, which is in $out/bin with the wrapper, but should be in the same location as the binary, in $out/share. I think this should fix my issues.