fix(ci): provision native Python runtime

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a06ba0-10aa-7ea0-b20a-4f3fac39efe9

.forgejo/workflows/runtime-contract.yaml

@@ -50,6 +50,18 @@ jobs:
           export UV_PYTHON_INSTALL_DIR="${work_dir}/uv-python"
           "${uv_bin}" python install 3.12
           python_bin="$("${uv_bin}" python find 3.12)"
+          if ! "${python_bin}" -c 'import ctypes; ctypes.CDLL("libgcc_s.so.1")' >/dev/null 2>&1; then
+            if command -v apk >/dev/null 2>&1; then
+              apk add --no-cache libgcc
+            elif command -v apt-get >/dev/null 2>&1; then
+              apt-get update
+              apt-get install -y libgcc-s1
+            else
+              echo "managed Python requires libgcc_s.so.1, but no supported package manager is available" >&2
+              exit 1
+            fi
+          fi
+          "${python_bin}" -c 'import ctypes; ctypes.CDLL("libgcc_s.so.1")'
 
           git clone "${FORGE_BASE}/${REPO_NAME}.git" "${work_dir}/rein-aharness"
           git -C "${work_dir}/rein-aharness" checkout --detach "${REPO_SHA}"