gnu-tar 1.28

If the maintainers are okay with this method of patching, it works on
my end and should pass the build bot. This complicates an otherwise
simple formula quite a bit, but apparently we should’ve been having
these issues from at least gnu-tar 1.27.1 but clearly, we weren’t. Not
really sure why 1.27.1 didn’t have the issues 1.28 is having, but this
patch fixes 1.28. It is reported upstream and may well end up in a
future release, but it needs to be confirmed that this patch doesn’t
break other non-OS X OS support before it can be folded in officially.