just use the prebuild image just as a normal compiled image.
install it with the JBB's halium-install script here
and get the ubports edge rootfs from here
./halium-install -p ut ubports-touch.rootfs-xenial-edge-armhf.tar.gz system.img
sudo fastboot flash boot halium-boot.img
some command are needed in order to get a working UT device (run as root).
chmod 666 /dev/kgsl-3d0
cat /var/lib/lxc/android/rootfs/ueventd*.rc|grep ^/dev|sed -e 's/^\/dev\///'|awk '{printf "ACTION==\"add\", KERNEL==\"%s\", OWNER=\"%s\", GROUP=\"%s\", MODE=\"%s\"\n",$1,$3,$4,$2}' | sed -e 's/\r//' > /etc/udev/rules.d/70-oneplus3.rules
chmod 4777 /usr/lib/dbus-1.0/dbus-daemon-launch-helper
chown root:messagebus /usr/lib/dbus-1.0/dbus-daemon-launch-helper
chmod u+s /usr/lib/dbus-1.0/dbus-daemon-launch-helper
adduser --force-badname --system --home /nonexistent --no-create-home --quiet _apt
mkdir -p /etc/system-image/config.d
mkdir /lib/firmware
ln -s /system/etc/firmware/* /lib/firmware/
# ln -s /firmware/image/* /lib/firmware/
echo manual | tee /etc/init/apparmor.override
cd /tmp
wget https://ci.ubports.com/job/pulseaudio-modules-droid/job/PR-1/8/artifact/pulseaudio-modules-droid-24_11.1.76+0~20190225000127.8~1.gbp826b96_armhf.deb
dpkg -i pulseaudio-modules-droid-24_11.1.76+0~20190225000127.8~1.gbp826b96_armhf.deb
sed -i -e "s/load-module module-droid-discover voice_virtual_stream=true/load-module module-droid-card-24/" /etc/pulse/touch.pa
For wifi:
echo sta > /sys/module/wlan/parameters/fwpath