Michał Górny 
Today's #Gentoo fun:
tmux fails to build with #libevent 2.2.1. It fails because of incompatible declaration of forkpty() in compat.h.
Looking into compat.h. forkpty() is declared there if HAVE_FORKPTY is false.
Looking into config.log. forkpty() is not found because configure tries to link random test programs to -levent_core@CMAKE_DEBUG_POSTFIX@.
At this point, you can guess what the problem is: https://github.com/libevent/libevent/issues/1459
*.pc files have unexpanded `@CMAKE_DEBUG_POSTFIX@` when built via autotools · Issue #1459 · libevent/libevent
To reproduce: $ ./autogen.sh $ ./configure -C $ grep POSTFIX *.pc libevent_core.pc:Libs: -L${libdir} -levent_core@CMAKE_DEBUG_POSTFIX@ libevent_extra.pc:Libs: -L${libdir} -levent_extra@CMAKE_DEBUG_...