Ignored or unknown attributes - Rebuild of the Debian archive with clang

"Ignored or unknown attributes" build failure(s)
clang 6.0

Versions: 2.9 - 3.0 - 3.1 - 3.2 - 3.3 - 3.4 - 3.4.2 - 3.5.0 - 3.6.0 - 3.8.1 - 3.9.1 - 4.0.1 - 5.0 - 6.0 - 8.0.1 - 9.0.1 - 10.0.0 - 11.0.0 - 12.0.1 - 13.0.0

Package	Version	Supposed error message	Full log	Bug report
ruby-prometheus-client-mmap	0.9.1-1	ruby.h:1771:1: error: unknown attribute '__error__' ignored [-Werror,-Wunknown-attributes]	Log

1 errors

Debian Package rebuild