This bug is in short a filter-flags-issue. qemu/kvms buildsystem links without CFLAGS (something that the devs of gcc even thinks is a bad idea) breaking everything depending on softmmu. Attaching patch for ebuild to fix this with a sed, and to remove all ugly/bad code that is not needed anymore after this fix.
Created attachment 208630 [details, diff] patch for kvm-ebuild, based on kvm-88-r1 This patch adds QEMU_CFLAGS and CFLAGS to LINK in rules.mak, removes the ${S} which repoman complains about, places filter-flags before ./configure so it actually makes a difference (since ./configure set the CFLAGS for the buildsystem, using filter-flags afterwards makes no difference) and split it in two since filter-flags currently only handles on flag at a time, and removed all of src_compile() since nothing in there is needed any more. This is tested and confirmed to work unlike the current ebuild in portage on several x86 and x86_64 machines.
fixed in qemu-kvm
fixed in app-emulation/qemu-kvm
