Cross-compilation does not work due to failing docker build step

Running `cross build` is not working due to a failure with a docker step:

```
$ cross build --target=armv7-unknown-linux-gnueabihf

info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'

stable-x86_64-unknown-linux-gnu unchanged - rustc 1.85.1 (4eb161250 2025-03-15)

info: checking for self-update
info: downloading component 'rust-src'
info: installing component 'rust-src'
DEPRECATED: The legacy builder is deprecated and will be removed in a future release.
Install the buildx component to build images with BuildKit:
https://docs.docker.com/go/buildx/

^[[DThe command '/bin/sh -c cd libgatekeeper && mkdir build && cd build && cmake .. -DCMAKE_TOOLCHAIN_FILE=/armv7-toolchain.cmake -DCMAKE_INSTALL_PREFIX=/usr/arm-linux-gnueabihf/ && make && make in
stall' returned a non-zero code: 1
Error:
0: could not run container
1: when building custom image
2: when building dockerfile
3: `docker build --label 'org.cross-rs.for-cross-target=armv7-unknown-linux-gnueabihf' --label 'org.cross-rs.workspace_root=/home/wilnil/Code/computersciencehouse/gatekeeper-door' --tag cross-custom-gatekeeper-door:armv7-u
nknown-linux-gnueabihf-4a201 --build-arg 'CROSS_DEB_ARCH=armhf' --build-arg 'CROSS_BASE_IMAGE=ghcr.io/cross-rs/armv7-unknown-linux-gnueabihf:0.2.5' --file ./Dockerfile /home/wilnil/Code/computersciencehouse/gatekeeper-door` f
ailed with exit status: 1
```

Running this command individually produces this output:

```
$ docker build --label 'org.cross-rs.for-cross-target=armv7-unknown-linux-gnueabihf' --label 'org.cross-rs.workspace_root=/home/wilnil/Code/computersciencehouse/gatekeeper-door' --tag cross-custom-gatekeeper-door:armv7-unknown-linux-gnueabihf-4a201 --build-arg 'CROSS_DEB_ARCH=armhf' --build-arg 'CROSS_BASE_IMAGE=ghcr.io/cross-rs/armv7-unknown-linux-gnueabihf:0.2.5' --file ./Dockerfile /home/wilnil/Code/computersciencehouse/gatekeeper-door

...

Step 10/13 : RUN cd libgatekeeper && mkdir build && cd build && cmake .. -DCMAKE_TOOLCHAIN_FILE=/armv7-toolchain.cmake -DCMAKE_INSTALL_PREFIX=/usr/arm-linux-gnueabihf/ && make && make install
---> Running in 61c9cc052cc5
CMake Warning:
Ignoring extra path from command line:

".."

CMake Error: The source directory "/libgatekeeper" does not appear to contain CMakeLists.txt.
Specify --help for usage, or press the help button on the CMake GUI.
The command '/bin/sh -c cd libgatekeeper && mkdir build && cd build && cmake .. -DCMAKE_TOOLCHAIN_FILE=/armv7-toolchain.cmake -DCMAKE_INSTALL_PREFIX=/usr/arm-linux-gnueabihf/ && make && make install' returned a non-zero code: 1
```