I think KDE and GNOME are exchanged. Reproducible: Always Steps to Reproduce: Actual Results: Under the USE section, add -gnome -gtk if you are using KDE, or add -kde -qt if you are going to use GNOME. Expected Results: Under the USE section, add -gnome -gtk if you are using __GNOME__, or add -kde -qt if you are going to use __KDE__.
it's not wrong, if you are a KDE user, you wouldn't want to compile gnome, gtk related softwares/compatibility in it. therefore, a -gnome -gtk is needed.
BTW, with a '-' sign infront of the flag which means to exclude, please check our USE-howto to understand more about gentoo :)