Use ubuntu 20.04 instead of 18.04

Author: electricbrass

.github/workflows/linux.yml

@@ -99,7 +99,7 @@ jobs:
     - name: Run build
       run: bash ci/fedora-buildgen.sh
   build-ubuntu-bionic:
-    name: Build (Ubuntu 18.04 LTS)
+    name: Build (Ubuntu 20.04 LTS)
     needs: pre_job
     if: ${{ needs.pre_job.outputs.should_skip != 'true' }}
     runs-on: ubuntu-latest
@@ -109,4 +109,4 @@ jobs:
     - name: Checkout submodules
       run: git submodule update --init --recursive
     - name: Run build
-      run: bash ci/ubuntu-bionic-buildgen.sh
+      run: bash ci/ubuntu-focal-buildgen.sh

ci/ubuntu-bionic-buildgen.sh ci/ubuntu-focal-buildgen.sh

@@ -7,5 +7,5 @@ IFS=$'\n\t'
 
 set -x
 
-docker build -t odamex -f ci/ubuntu-bionic.Dockerfile .
+docker build -t odamex -f ci/ubuntu-focal.Dockerfile .
 docker run --rm odamex

ci/ubuntu-bionic.Dockerfile ci/ubuntu-focal.Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:18.04
+FROM ubuntu:20.04
 
 WORKDIR odamex