The situation is I want to add conditional macro to control bootstrap.
Because I want to create RSpec modularity, and want to control bootstrap from modulemd file macro.
But the rpms/rubygem-rspec-core owner does not like adding the conditional macro.
The reason makes sense to me. And I want to respect his opinion.

https://src.fedoraproject.org/rpms/rubygem-rspec-core/pull-request/1

%{?_with_bootstrap: %global bootstrap 1}

Actually I never like this approach, because I cannot check what build option or so is used for the binary rpm by checking the srpm afterwards.

The solution is

1. Build rpms/rubygem-rspec with another repository, setting /data/components/rpms/repository as the repository.
2. Edit the PRM spec file from modularity config file. This feature might be to add /data/components/rpms/cmd element to use UNIX shell command.
   This feature has been used in a tool to build Software Collection.
   https://github.com/sclorg/rhscl-rebuild-recipes/blob/master/ror.yml#L46

What do you think?