use ubuntu 18.04 for artifact build process;

Author: greenhat

.github/workflows/release.yml

@@ -13,7 +13,7 @@ jobs:
             os: ubuntu-20.04
             build_tool: cross # Use https://github.com/cross-rs/cross for ARM
           - target: x86_64-unknown-linux-gnu
-            os: ubuntu-20.04
+            os: ubuntu-18.04
             build_tool: cargo
           - target: x86_64-apple-darwin
             os: macos-latest