Run github action on Ubuntu 20.04

Author: BitProcessor

.github/workflows/build.yaml

@@ -11,19 +11,12 @@ jobs:
 
   build:
 
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     if: "!contains(github.event.head_commit.message, '[skip ci]')"
 
     steps:
     - uses: actions/checkout@v2
 
-    # - name: Get util-linux version
-    #   id: get_util_linux
-    #   run: |
-    #     version=$(curl --silent https://api.github.com/repos/karelzak/util-linux/tags | jq -r '.[0].name' | sed -e 's/^v//')
-    #     echo "::debug::get util-linux version ${version}"
-    #     echo "::set-output name=version::${version}"
-
     - name: Set up QEMU
       uses: docker/setup-qemu-action@v1
 
@@ -41,7 +34,6 @@ jobs:
       id: docker_build
       uses: docker/build-push-action@v2
       with:
-        # build-args: UTIL_LINUX_VER=${{ steps.get_util_linux.outputs.version }}
         platforms: linux/amd64,linux/arm64
         tags: |
           ghcr.io/bitprocessor/nsenter:latest