Set install_dir (per Ephil012's suggestion)

Set install_dir to a correct value for macOS. Thanks to @Ephil012 for pointing out this is needed.

webui-macos-env.sh

@@ -9,6 +9,7 @@ then
     python_cmd="python3.10"
 fi
 
+export install_dir="$HOME"
 export COMMANDLINE_ARGS="--skip-torch-cuda-test --no-half --use-cpu interrogate"
 export TORCH_COMMAND="pip install torch==1.12.1 torchvision==0.13.1"
 export K_DIFFUSION_REPO="https://github.com/brkirch/k-diffusion.git"