flesh out clang announcement

Author: h-vetinari

news/2024-04-09-clang-everywhere.md

@@ -0,0 +1,36 @@
+# Clang now available as compiler for all platforms
+
+Our compiler stack per platform generally uses the "default" compiler for that
+platform, see e.g. [here](https://conda-forge.org/docs/maintainer/infrastructure/#compilers-and-runtimes).
+
+In practice, this meant that
+```
+c_compiler:
+  - gcc         # [linux]
+  - clang       # [osx]
+  - vs2019      # [win]
+cxx_compiler:
+  - gxx         # [linux]
+  - clangxx     # [osx]
+  - vs2019      # [win]
+```
+was the only possible choice for C/C++ compilers.
+
+Recently, we finished adding preliminary support `clang` / `clangxx` as
+C/C++ compilers also on osx and windows, starting from clang 18.
+This is still very fresh, so bugs are possible, and we ask not to change
+the default compilers on feedstocks unless there are compelling reasons.
+
+In any case, it is now possible to use the following configuration in
+`recipe/conda_build_config.yaml`:
+```
+# please consult @conda-forge/core before doing this
+c_compiler:
+  - clang
+c_compiler_version:
+  - 18
+cxx_compiler:
+  - clangxx
+cxx_compiler_version:
+  - 18
+```