rakudo-zef-0.5.3-2.fc30 has this in the build.log: mangling shebang in /usr/lib64/perl6/vendor/bin/zef-j from /usr/bin/env perl6-j to #!/usr/bin/perl6-j Note that /usr/bin/perl6-j is not provided by any package and hence such shebang makes no sense.
This is not a bug it is a feature. :-) For radudo-perl6 in Fedora is only the moar backend provided. So there is no perl6-j. The zef build recognize that and do not provide a zef-j, so that is only a message during the build that can be ignored. The Fedora rakudo-zef package do not provide an zef-j file. I do not know much about Java. But if you know someone who know much about Java and packaging Java modules and would like to help me to build a npq-j and rakudo-j package and do an review than I could try to get this packages in Fedora. Also anyone else are free to do this.
OK, thanks for explaining. Note: The package does not require /usr/bin/perl6-j, so it should install OK.