LDC 1.42.0

[kinke]

Glad to announce LDC 1.42. Some major changes:

* Based on D 2.112.1+ (today's upstream stable).
* Support for LLVM 21; the prebuilt packages use v21.1.8.
* New prebuilt package for Alpine Linux aarch64.
* `ldc2.conf` can now be a directory. All the files inside it, 
ordered naturally, will be concatenated and treated like a big 
config. This enables simpler config extensions (e.g., for 
cross-compilation targets) by adding files instead of modifying a 
file. This feature comes with breaking CMake changes.
* Breaking change for dcompute: The special `@kernel` UDA is now 
a function and requires parentheses.
* New `--fdebug-prefix-map` command-line option to aid 
reproducible builds.

Full release log and downloads: 
https://github.com/ldc-developers/ldc/releases/tag/v1.42.0

Thanks to all contributors & sponsors!