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.
This raises the versions of bundled software, providing e.g.
autoconf 2.71, which is needed for Python 3.12.
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 generated tar archives contain the uid/gid of the builder,
if unpacked as root on another system those will denote nothing
or an unexpected user/group.
The expectation would be uid/gid = 0.
Use a simple enough tar format as well.
The Mac version of tar (bsdtar?) does not support those flags,
for CI the separate gnu-tar is installed.
Ubuntu 20.04 comes with CMake 3.16, so there's no need to install
a custom version of CMake for now (for LLVM 16.x; LLVM 17 will have
the requirement raised to CMake 3.20 though).
Also drop the workaround for git issues in the old version in
Ubuntu 18.04.
The latest releases that are built on GitHub Actions without
docker are based on Ubuntu 20.04 anyway, so there's less demand
for building this with an older version for the sake of
compatibility of the built binaries. For users using the built
docker image as such, having it based on a newer base distribution
is beneficial.
Martin Storsjö