Enhancements:
-------------

* expose time and datetime modules in jinja2 context, for use in meta.yaml  #2513
* jinja: permit recipes to check for existence of a variable without erroring  #2529
* add method for getting all variant values used by a recipe, not just those variants with more than one value.  #2531

Bug fixes:
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* allow SSL_NO_PROXY env var to disable SSL checking on proxied connections  #2505
* Fix source hoisting issues (incorrectly flattening directory structure of extracted archives)  #2507
* Fix build env for output getting lost when output name == top-level name  #2511
* add global pin_run_as_build for R (x.x.x) to keep legacy R pinning behavior  #2518
* Fix path conversion issues going from windows to unix  #2522
* only insert variant versions when testing runtime availability for packages that are also present in build (not just run)  #2527