ci: use Ubuntu Jammy for Windows CI

This means we'll compile using GCC 10.3.x and mingw-w64 8.0.0 which
better matches our Guix release environment.

Author: fanquake

.cirrus.yml

@@ -176,10 +176,10 @@ task:
     QEMU_USER_CMD: ""  # Disable qemu and run the test natively
 
 task:
-  name: 'Win64 [unit tests, no gui tests, no boost::process, no functional tests] [focal]'
+  name: 'Win64 [unit tests, no gui tests, no boost::process, no functional tests] [jammy]'
   << : *GLOBAL_TASK_TEMPLATE
   container:
-    image: ubuntu:focal
+    image: ubuntu:jammy
   env:
     << : *CIRRUS_EPHEMERAL_WORKER_TEMPLATE_ENV
     FILE_ENV: "./ci/test/00_setup_env_win64.sh"

ci/test/00_setup_env_win64.sh

@@ -7,7 +7,7 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_win64
-export DOCKER_NAME_TAG=ubuntu:20.04  # Check that Focal can cross-compile to win64
+export DOCKER_NAME_TAG=ubuntu:22.04  # Check that Jammy can cross-compile to win64
 export HOST=x86_64-w64-mingw32
 export DPKG_ADD_ARCH="i386"
 export PACKAGES="python3 nsis g++-mingw-w64-x86-64 wine-binfmt wine64 wine32 file"