scripts: Use a separate defconfig for NSU build

Bloat? sure, but much more saner than having to maintain a patchfile when we could be switching around KernelSU forks (I.e RissuKSU and KernelSU-Next)
Also, now make the KSU-only bypass also trigger when local=true, as I am already compiling locally with -su soooo

This commit message should make it clear that the buildscripts is aimed for my personal preferences
Don't squash this for maintainabilty reasons (still easier than a patchfile)

Signed-off-by: Yahya Wessam <yahyawessam2002@gmail.com>

Author: vbajs