tweak what is backported, as requested

- don't backport `pyproject.toml` or related changes
- install some additional -dev packages with `apt-get` for CodeQL
- run CodeQL in a python venv

.github/workflows/codeql-analysis.yml

@@ -47,8 +47,9 @@ jobs:
             ${{ runner.os }}-
     - name: Install requirements
       run: |
-       sudo apt-get update
+        sudo apt-get update
-       sudo apt-get install -y libacl1-dev
+        sudo apt-get install -y pkg-config build-essential
+        sudo apt-get install -y libssl-dev libacl1-dev libxxhash-dev liblz4-dev libzstd-dev
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v1
@@ -60,6 +61,8 @@ jobs:
         # queries: ./path/to/local/query, your-org/your-repo/queries@main
     - name: Build and install Borg
       run: |
+        python3 -m venv ../borg-env
+        source ../borg-env/bin/activate
         pip3 install -r requirements.d/development.txt
         pip3 install -e .
     - name: Perform CodeQL Analysis

pyproject.toml

@@ -1,3 +0,0 @@
-[build-system]
-requires = ["setuptools", "pkgconfig", "Cython!=0.27"]
-build-backend = "setuptools.build_meta"

setup.py

@@ -19,7 +19,6 @@ try:
 except ImportError:
     cythonize = None
 
-sys.path += [os.path.dirname(__file__)]
 import setup_checksums
 import setup_compress
 import setup_crypto