QEMU doesn't hook execve anyway, at least not upstream -- when a QEMU emulated process invokes another we rely on the binfmt-misc magic to cause the kernel to run QEMU on the child. We don't special case "the binary being exec'd seems to also be for the guest".
It looks like maybe you've made some local patches to QEMU that relate to execve?
It looks like maybe you've made some local patches to QEMU that relate to execve?