Add note about extra build requirements.

Author: dnwpark

gel/_internal/arch.md

@@ -121,15 +121,22 @@ Run `python tools/gen_models.py` to generate test models into your virtual envir
 ### Prerequisites
 
 1. gel development VM with gel server binary in PATH
-2. Install with: `pip install -e .`
-3. **Critical**: Edit `.pth` files because editable wheel install is broken:
+2. Ensure additional requirements are installed
+
+  ```bash
+  pip install setuptools==70
+  pip install cython
+  ```
+
+3. Install with: `pip install -e .`
+4. **Critical**: Edit `.pth` files because editable wheel install is broken:
 
    ```bash
    python -c 'import pathlib, gel; print(pathlib.Path(gel.__path__[0]).parent)' > \
      $(python -c 'import site; print(site.getsitepackages()[0])')/gel.pth
    ```
 
-4. Set environment variables for gel server path if needed
+5. Set environment variables for gel server path if needed
 
    * If you want to use the dev server in your dev Gel environment:
 
@@ -147,6 +154,8 @@ Run `python tools/gen_models.py` to generate test models into your virtual envir
 
      and you should be able to just run `$ pytest`.
 
+    Note: make sure you are not using a system wide `pytest` install!
+
 
 ### Running Tests