Created attachment 867798 [details] build log without the patch execinfo isn't a thing in musl it seems, so I patched it out.
Created attachment 867799 [details] emerge --info '=gui-wm/hyprland-0.28.0-r1::gentoo'
Created attachment 867800 [details] emerge -pqv '=gui-wm/hyprland-0.28.0-r1::gentoo'
Created attachment 867801 [details, diff] patch
Upstream report: https://github.com/hyprwm/Hyprland/issues/1740
Created attachment 873859 [details] gui-wm/hyprland-0.31.0 build without a patch
As Pedro has confirmed upstream have solved this so no longer relevant.