If building mrxvt you have only the option to use the default setting, which has been set with mrxvt-0.5.1, to build with rounded tabs. If you want to use squared tabs there is no use flag in the current mrxvt ebuild 0.5.4 to enable squared tabs. Reproducible: Always
Created attachment 284003 [details, diff] patch for squared tabs
This package is now orphan: http://my.opera.com/pacho/blog/2012/11/27/about-maintainer-needed
This is minor fix. Are you still interested?