Merge pull request #1571 from conda-forge/beckermr-patch-1

ENH announcement about cos7 docker images

Author: beckermr

src/user/announcements.rst

@@ -8,6 +8,16 @@ Our announcements are published to an RSS feed `here <https://conda-forge.org/do
 2021
 ----
 
+:2021-12-02: CentOS 7 docker images are now the default
+
+    We are moving all ``conda-forge`` ``linux-64`` jobs to use CentOS 7-based docker images. 
+    This will help users avoid ``conda/mamba`` solver errors where dependencies that need 
+    CentOS 7 cannot be installed. Importantly, our compiler stack will still default to using 
+    a CentOS 6 sysroot unless the recipe explicitly lists the CentoOS 7 sysroot package. This 
+    build configuration means that our core system ABI on linux will remain largely CentOS 6-compatible,
+    keeping support for older systems largely intact. We will reconsider moving the default ABI to 
+    CentOS 7 at a later date.
+
 :2021-11-17: ``cloud.drone.io`` no longer working
 
     The ``cloud.drone.io`` service we use for ``aarch64`` builds is no longer accepting our API