build: improve justfile and debian/rules

debian/rules

@@ -1,33 +1,15 @@
 #!/usr/bin/make -f
 
-DESTDIR = debian/cosmic-session
-CLEAN ?= 1
-VENDOR ?= 1
+export DESTDIR = debian/cosmic-session
 
 %:
 	dh $@
 
-override_dh_installgsettings:
-	dh_installgsettings --priority=50
-
-override_dh_shlibdeps:
-	dh_shlibdeps --dpkg-shlibdeps-params=--ignore-missing-info
-
 override_dh_auto_clean:
-	if test "${CLEAN}" = "1"; then \
-		cargo clean; \
-	fi
-
-	if ! ischroot && test "${VENDOR}" = "1"; then \
-		mkdir -p .cargo; \
-		cargo vendor --sync Cargo.toml | head -n -1 > .cargo/config.toml; \
-		echo 'directory = "vendor"' >> .cargo/config.toml; \
-		tar pcf vendor.tar vendor; \
-		rm -rf vendor; \
-	fi
+	ischroot || just vendor
 
 override_dh_auto_build:
-	just rootdir=$(DESTDIR) debug=$(DEBUG) vendor=$(VENDOR)
+	test -e vendor.tar && just build-vendored || just
 
 override_dh_auto_install:
 	just rootdir=$(DESTDIR) install