Hi Chris,
Unfortunately I was not able to reproduce your issue.
I did a checkout following your instructions and used this manifest: https://github.com/seL4/camkes-vm-examples-manifest/blob/e37e3e259ff7dd5060e...
I changed the FPU save method, and ran the resulting images using the same qemu line as you. I booted to the login prompt in about 5 seconds from when the seL4 kernel loaded.
The images I built are here: https://cloudstor.aarnet.edu.au/plus/s/IPH5dU4Ri0lnZxb%E2%80%8B My output is attached.
$ qemu-system-x86_64 --version QEMU emulator version 2.12.0 (Debian 1:2.12+dfsg-3) Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
Kind regards, Kent.