docker: Bump the base images to Ubuntu 24.04

As the releases are built (without a surrounding extra container)
on GitHub Actions these days, we don't need to hold the docker
images back to an old version for the sake of compatibility;
instead, updating to a newer version provides more modern tools
for users of the docker image.

The script release.sh, which earlier was used for building releases,
uses docker for doing clean isolated builds, and thus needs to be
updated with the distro version used in the dockerfiles.

Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:22.04
+FROM ubuntu:24.04
 
 RUN apt-get update -qq && \
     DEBIAN_FRONTEND="noninteractive" apt-get install -qqy --no-install-recommends \

Dockerfile.dev

@@ -1,4 +1,4 @@
-FROM ubuntu:22.04
+FROM ubuntu:24.04
 
 RUN apt-get update -qq && \
     DEBIAN_FRONTEND="noninteractive" apt-get install -qqy --no-install-recommends \

Dockerfile.toolchain

@@ -1,4 +1,4 @@
-FROM ubuntu:22.04
+FROM ubuntu:24.04
 
 RUN apt-get update -qq && \
     DEBIAN_FRONTEND="noninteractive" apt-get install -qqy --no-install-recommends \

release.sh

@@ -29,7 +29,7 @@ fi
 
 time docker build -f Dockerfile . -t mstorsjo/llvm-mingw:latest -t mstorsjo/llvm-mingw:$TAG
 
-DISTRO=ubuntu-22.04-$(uname -m)
+DISTRO=ubuntu-24.04-$(uname -m)
 docker run --rm mstorsjo/llvm-mingw:latest sh -c "cd /opt && mv llvm-mingw llvm-mingw-$TAG-ucrt-$DISTRO && tar -Jcvf - --format=ustar --numeric-owner --owner=0 --group=0 llvm-mingw-$TAG-ucrt-$DISTRO" > llvm-mingw-$TAG-ucrt-$DISTRO.tar.xz
 
 if [ -n "$NATIVEONLY" ]; then