This is an auto-filled bug because sys-cluster/ceph fails to compile. The issue was originally discovered on arm64, but it may be reproducible on other arches as well. If you think that a different summary clarifies the issue better, feel free to change it. Attached build log and emerge --info.
Created attachment 636752 [details] build.log.bz2 build log and emerge --info
Try 14.2.9-r1 please, 14.2.7 is only in the tree because of arm64 keyword
15.2.1-r1 works for me