We need to have USE=static-libs because this package install '.a' files: /usr/lib64/libtokyocabinet.a /usr/lib64/libtokyocabinet.so /usr/lib64/libtokyocabinet.so.9 /usr/lib64/libtokyocabinet.so.9.11.0
Make it so then.
See also: https://projects.gentoo.org/qa/policy-guide/installed-files.html#pg0302