Use new Ruby Macros since they are also now supported on 13.1
Remove nokogiri build logs

In 13.2 Nokogiri creates build logs during build of the native
extensions which trigger the following rpmlint errors:

machinery.x86_64: E: file-contains-buildroot (Badness: 10000) /usr/lib64/ruby/gems/2.1.0/gems/machinery-tool-1.0.2/bundle/ruby/2.1.0/extensions/x86_64-linux/2.1.0/nokogiri-1.6.3.1/gem_make.out
machinery.x86_64: E: file-contains-buildroot (Badness: 10000) /usr/lib64/ruby/gems/2.1.0/gems/machinery-tool-1.0.2/bundle/ruby/2.1.0/extensions/x86_64-linux/2.1.0/nokogiri-1.6.3.1/mkmf.log

Removing the logs fixes the issue.
Add nokogiri log removal entry to RPM_CHANGES
Merge pull request #365 from SUSE/adapt_rpm_spec_for_13_2

Adapt rpm spec for 13 2