devel/ruby-subversion: fix build on GCC architectures

Ruby needs newer compiler:
subversion/bindings/swig/ruby/libsvn_swig_ruby/swigutil_rb.c: In function 'callback_rescue':
subversion/bindings/swig/ruby/libsvn_swig_ruby/swigutil_rb.c:1628:38: error: 'ruby_errinfo' undeclared (first use in this function); did you mean 'rb_errinfo'?
1628 | ruby_errinfo,

MFH: 2020Q4