dev-libs/libatomic_ops is not runtime depend, only build time. It installs only headers and static libs.
Fixed in 7.2d-r1, thanks for the report.
Now revdep-rebuild reports: broken /usr/lib/libcord.la (requires -latomic_ops) broken /usr/lib/libgccpp.la (requires -latomic_ops)
(In reply to sf from comment #2) > Now revdep-rebuild reports: > > broken /usr/lib/libcord.la (requires -latomic_ops) > broken /usr/lib/libgccpp.la (requires -latomic_ops) 7.2e is now stable which doesn't exhibit this issue.