fix(deb): disable pip build isolation for dh-virtualenv

PEP 517 build isolation hides errors and fails on setup.py.
Using --no-build-isolation lets pip use the venv's setuptools directly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: flound1129

debian/rules

@@ -20,7 +20,8 @@ override_dh_virtualenv:
 	dh_virtualenv \
 		--install-suffix deluge \
 		--use-system-packages \
-		--package squall-common
+		--package squall-common \
+		--extra-pip-arg '--no-build-isolation'
 
 execute_before_dh_virtualenv:
 	echo "$(VERSION)" | sed 's/~/./' > RELEASE-VERSION