as part of the build process breeze-icons builds qrcAlias to generate the rcc file, in a cross-compile setup qrcAlias would have to be built for the build architecture rather than the host architecture (i.e. what is being built for). e.g. if you cross-build on x64 for arm you'd need qrcAlias to be built for x64 so you can run it at build time. the way it is built now is for arm making it not runable. workaroundable by not cross-compiling the icons as the generated data one could build it on x64 and use on arm. this does however mean that you couldn't build the rcc without having a qtbase build for the build arch (so you can build the icons) AND a qtbase for the host arch (for the app that uses the rcc)
The component Icons is for icon design stuff. what you wrote is something devel specific I didn't understood anything.
Any chance you'd be interested i fixing this, Harald?
Not particularly
There is a patch available at https://build.opensuse.org/package/view_file/windows:mingw:win32/mingw32-breeze5-icons/0001-extend-generating-of-qrcalias.patch?expand=1, which provides generating qrcAlias when cross compiling.