So, here's a short how to for compiling the source code provided by Garmin-asus. Please note there may be a step or two missing. I'll be updating this later when I get a chance to start from scratch and compile a better How To.

The originial directions for porting a kernel can be found here:

1. Download the v.5.0.70 kernel source from garmin-asus.
Which can be found here:

# curl >~/bin/repo
# chmod a+x ~/bin/repo
# mkdir <Android source dir> && cd <Android source dir>
# repo init -u git:// -b froyo
# repo sync
# export PATH=$PATH:~/<Android source dir>/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin
3. Copy the kernel folder from Garminfone_T-Mobile_5.0.70.tar.gz.
4. Place it in <Android source dir>
5. Rename it, 'asus-kernel'
# export ARCH=arm
# export CROSS_COMPILE=arm-eabi-
# export KERNEL_DIR=/full/path/to/asus-kernel
7. Download my found in my post:
8. Extract asus_defconfig
9. Place asus_defconfig in <Android source dir>/asus-kernel/arch/arm/configs
# cd <asus-kernel source dir>
# make asus_defconfig
It should work, I pulled what I did from memory. So like I said, if you're having issues, give me some time to get together a better How To.