I'm unsure why, but it fails on icc.
https://rubyci.org/logs/rubyci.s3.amazonaws.com/icc-x64/ruby-master/log/20200408T220004Z.log.html.gz
```
In file included from ../../.././include/ruby/3/core.h(32),
from ../../.././include/ruby/ruby.h(28),
from cxxanyargs.cpp(1):
../../.././include/ruby/3/core/rtypeddata.h(163): error: return value type does not match the function type
RUBY3_UNREACHABLE_RETURN(NULL);
```
8ab4c55e7a