Bug 599402 requested an ~arm keyword on x11-libs/xcb-util-xrm in Nov 2016, which at the time only had version 1.0. The ~arm keyword was added in late February, two months after version 1.2 had entered the tree. Please add an ~arm keyword to =x11-libs/xcb-util-xrm-1.2 I have seen a lot of instances of this problem from arm in particular. Please modify your workflow to ensure that you are keywording the newest version.
~arm added to the latest version.