Fix fixing JRuby shebangs on macOS

LC_CTYPE is "utf-8" on macOS, which instructs utilities like `tr` to expect Unicode input. However, in case of binary files, which we here explicitly guard against, the utility will fail because of invalid input encoding.

The solution is to set LC_CTYPE=C which effectively removes the expectation around input encoding and allows `tr` to process the input byte-by-byte.