ruby-modules is not required to depend on ruby binary
if ruby binar needs ruby-modules, that's fine
build fails without ruby binary:
executable host ruby is required. use --with-baseruby option.
BuildRequires: openssl-devel
BuildRequires: pkgconfig
BuildRequires: readline-devel >= 4.2
-%{!?with_bootstrap:BuildRequires: ruby-modules}
+%{!?with_bootstrap:BuildRequires: ruby}
BuildRequires: sed >= 4.0
BuildRequires: yaml-devel
%if %{with tk}