Windows: new format for msys packages is zstd compressed not xz
When the toolchains were bumped for GHC 9 it didn't take into account a change in format for the packages from msys2. This resulted in a toolchain being created without a crt or headers.
From the list of packages I see that a new download zstd
was
added as a toolchain package, however I think the misunderstanding
is that the zlib we have in the package atm is for the GCC LTO
streaming compression which uses zlib. i.e. zlib is a dependency
of GCC. zstd is not. So I believe that unused..
Locally you wouldn't notice it because maintainer-clean
didn't
remove the ghc-tarballs
folder. So you ended up with a franken
build. This has now been changed.
Fixes #18845 (closed) and the CI.
You need a recent msys2 for this to work or you need to install
zstd pacman -S zstd
.