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

* incorporate libarchive to support more compression formats (adds libarchive as a package dep)  #3163
* add build/ignore_verify_codes key to allow recipes to ignore specific conda-verify error codes  #3179

Bug fixes:
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* fix JSON string encoding error in index cache reading  #3156
* restore --variants CLI flag for specifying variants  #3168
* handle empty build section in output  #3175
* add mro-base_impl as something that causes mro build strings  #3163
* fix skeleton PyPI inappropriately dropping package case (needed for URLs)  #3163
* fix packages from earlier loops with multiple outputs being removed prior to later loops  #3185
* fix conda-index not removing entries from index that no longer exist on disk  #3186 #3188
* clean up tempfiles after indexing  #3187
* fix indexing of specific subdirs  #3190
* fix pypi skeleton when python constraint has no operator  #3191
* fix issues testing packages and recipe folders when done separately from build  #3192
* fix source looking for patches in wrong folder when dealing with outputs  #3194

Contributors:
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* @dpryan79
* @gabm
* @mbargull
* @mingwandroid
* @msarahan
* @nehaljwani