#2364: use Ubuntu 22.04 in documentation build

Author: cz4rs

.github/workflows/build-docs.yml

@@ -14,10 +14,10 @@ jobs:
     env:
       REPO: lifflander1/vt
       ARCH: amd64
-      UBUNTU: 18.04
+      UBUNTU: 22.04
       COMPILER_TYPE: gnu
-      COMPILER: gcc-8
-      HOST_COMPILER: gcc-8
+      COMPILER: gcc-11
+      HOST_COMPILER: gcc-11
       BUILD_TYPE: release
       ULIMIT_CORE: 0
       VT_LB: 1

ci/docker/ubuntu-gnu-docs.dockerfile

@@ -1,5 +1,6 @@
 ARG arch=amd64
-FROM ${arch}/ubuntu:18.04 as base
+ARG ubuntu=22.04
+FROM ${arch}/ubuntu:${ubuntu} as base
 
 ARG proxy=""
 ARG compiler=gcc-8