Exract version by using the included "make kernelversion" instead of writing
a custom grep script that was used before.
VERSION=$(grep '^VERSION' Makefile | grep -Eo '[0-9]{1,4}')
PATCHLEVEL=$(grep '^PATCHLEVEL' Makefile | grep -Eo '[0-9]{1,4}')
SUBLEVEL=$(grep '^SUBLEVEL' Makefile | grep -Eo '[0-9]{1,4}')
$ make kernelversion
4.19.36