Add news about the default OSX deployment target for Rust

Author: xhochy

news/2024-01-29-rust-175-osx-sdk.md

@@ -0,0 +1,21 @@
+# Rust 1.75 requires setting newer MACOSX_DEPLOYMENT_TARGET
+
+With the release of `rust 1.75`, we now require setting the minimal
+`MACOSX_DEPLOYMENT_TARGET` to at least `10.12`. You can do this by appending
+`recipe/conda_build_config.yaml` with the following content:
+
+```
+MACOSX_DEPLOYMENT_TARGET:  # [osx and x86]
+  - '10.12'                # [osx and x86]
+```
+
+You should also add a run dependency on the respective OSX version:
+
+```
+  run:
+    - __osx >={{ MACOSX_DEPLOYMENT_TARGET|default("10.9") }}  # [osx and x86_64]
+```
+
+The latter is also set automatically via a `run_exports` of
+the `compiler('rust')` package, but we add this line if you would increase
+the deployment target later in the feedstock for unrelated reasons.