v8-5.2.258-1 is not built with $RPM_OPT_FLAGS. 3.14.5.10-23 did not have this problem. https://kojipkgs.fedoraproject.org/packages/v8/5.2.258/1.fc25/data/logs/x86_64/build.log https://kojipkgs.fedoraproject.org/packages/v8/3.14.5.10/23.fc24/data/logs/x86_64/build.log
Good catch. It is now in -2.