Update buildkit.md

docs/tools/buildkit.md

@@ -6,6 +6,36 @@ Many of these tools are commonly used by web developers, so you may have already
 
 This is the same collection of tools which manages the test/demo/release infrastructure for civicrm.org.
 
+## Supported Operating Systems
+
+Currently BuildKit includes [specific, tested install steps](https://github.com/civicrm/civicrm-buildkit/blob/e278123c2a5edb525a01c816283d30b882aa8fab/bin/civi-download-tools#L329) for the following Ubuntu and Debian operating system releases - note that recently removed versions are shown in this list for information and are marked in the final column.
+
+## Ubuntu
+ Version | Codename | Release Date | EOL Date | Buildkit Removal |
+--------- | ------------ | -------------- | ---------- | ------------------------- |
+19.04 | Disco Dingo | April 2019 | January 2020 | June 2020 |
+18.10 | Cosmic Cuttlefish | October 2018 | July 2019 <sup>&#x1F534;</sup> | January 2020 |
+18.04 | Bionic Beaver | April 2018 | April 2023 | October 2023 |
+17.10 | Artful Aardvark | October 2017 | July 2018 <sup>&#x1F534;</sup> | January 2019 <sup>&#x2705;</sup> |
+17.04 | Zesty Zapus<sup>*</sup> | April 2017 | January 2018 <sup>&#x1F534;</sup> | July 2018 <sup>&#x2705;</sup> |
+16.10 | Yakkety Yak<sup>*</sup> | October 2016 | July 2017 <sup>&#x1F534;</sup> | January 2018 <sup>&#x2705;</sup> |
+16.04 | Xenial Xerus | April 2016 | April 2021 | October 2021 |
+14.04 | Trusty Tahr | April 2014 | April 2019 <sup>&#x1F534;</sup> | October 2019 <sup>&#x2705;</sup> |
+12.04 | Precise Pangolin | April 2012 | April 2017 <sup>&#x1F534;</sup> | October 2017 <sup> &#x2705;</sup> |
+
+<sup>*</sup> = Reuses installation steps for Xenial Xerus.
+<sup>&#x1F534;</sup> = Is currently EOL
+<sup>&#x2705;</sup> = Has been removed from BuildKit
+
+## Debian
+Version | Codename | Release Date | EOL Date | BuildKit Removal |
+--------- | ------------ | -------------- | ---------- | ------------------ |
+10 | Buster | July 2019 | 202x | Unknown |
+9 | Stretch | June 2017 | 2022 | Unknown |
+8 | Jessie | April 2015 | June 2020 | September 2020 |
+
+!!! warning
+    Our current policy is that these specific install steps will be removed from BuildKit when they reach their End Of Live (EoL) date       plus 6 months. See [this issue](https://github.com/civicrm/civicrm-buildkit/issues/432) for discussion/information.
 
 ## Installation