USERPATCHES_PATH is ignored/not working

### What happened?

I am using the USERPATCHES_PATH so that my patches can be outside of the build repository and under my own git.

However the launched docker is still bind-mounting the build/userpatches as armbian/userpatches and the USERPATCHES_PATH are simply not mounted in the docker container.

so, I cannot do any user customization at all.

Tested both on main and on stable (v23.11.2)

### How to reproduce?

PATCHES=$(pwd)/userpatches

cd build

./compile.sh \
BOARD=odroidxu4 \
RELEASE=jammy \
BRANCH=current \
KERNEL_CONFIGURE=no \
BUILD_MINIMAL=yes \
BUILD_DESKTOP=no \
CONSOLE_AUTOLOGIN=no \
USERPATCHES_PATH=$PATCHES

### Branch

main (main development branch)

### On which host OS are you observing this problem?

Jammy

### Relevant log URL

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct