fix rustup

tests/test_packaging.py

@@ -78,3 +78,11 @@ def test_all_three_linux_families_are_always_published():
     for name in ("DEBIAN-BUILD-INFO.txt", "RHEL-BUILD-INFO.txt", "SUSE-BUILD-INFO.txt"):
         assert name in build
         assert name in init
+
+
+def test_rustup_installation_and_runtime_cargo_home_are_consistent():
+    dockerfile = (ROOT / "Dockerfile").read_text()
+    assert "CARGO_HOME=/opt/cargo" in dockerfile
+    runtime_env = dockerfile.split("ENV DATA_DIR=/var/lib/rustbox-package-builder", 1)[1]
+    assert "CARGO_HOME=/var/lib/rustbox-package-builder/cargo" not in runtime_env
+    assert "CARGO_TARGET_DIR=/var/lib/rustbox-package-builder/cargo/target" in runtime_env