This is an auto-filed bug because dev-libs/criterion misses USE=static-libs and installs '.a' files.
The issue was originally discovered on amd64, but it may be reproducible on other arches as well.
The issue was discovered on the version reported in the summary but it may be reproducible on other versions as well. The best solution is avoid to build the '.a' files by touching the configure. In case the buildsystem makes your life hard, a good compromise would be just remove the files.
NOTE: If you want to change the summary, to avoid auto-filed duplicates, please at least keep the word 'static-libs'
libarchive_tinderbox has reproduced this issue with version 2.4.1 - Updating summary.