LDC 1.42.0-beta1

[kinke]

Glad to announce the first beta for LDC 1.42, to sweeten your 
holidays! :) Some major changes:

* Based on early D 2.112.0 (recent upstream stable). As it's been 
some time since v2.111, the number of changes is significantly 
higher than usual!
* Support for LLVM 21. The prebuilt packages still use v20 for 
now.
* 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.

Full release log and downloads: 
https://github.com/ldc-developers/ldc/releases/tag/v1.42.0-beta1

Please help test, and thanks to all contributors & sponsors!