Gentoo's Bugzilla –
Attachment 558474 Details for
Bug 673718net-mail/mailutils-3.4-r2 - In file included from common.c:95: /usr/include/bits/wchar2.h: In function ‘wcrtomb’: /usr/include/bits/wchar2.h:448:3: error: #error "Assumed value of MB_LEN_MAX wrong"