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

* Improve "BUILD" environment variable value (especially on powerpc)  #2615
* Implement CentOS 7 ppc64le distro for conda skeleton rpm  #2615
* Improve handling of outputs that use the build/skip key to skip building  #2616

Bug fixes:
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* Don't loop in all zipped keys when collecting used vars.  Leave it to consumers to decide what to do.  #2612
* Fix run_exports using pin_subpackage not applying versioning for the implicit top-level output  #2613
* Fix run_exports not applying to build-time environment creation for top-level recipe (as opposed to outputs)  #2613
* Fix CRAN skeleton to better use host/build envs appropriately  #2614
* fix outputs not loading hash input info from files at test time correctly, leading to incorrect hashes and unresolved packages.  #2616