It failed to build on arm64:

http://buildd.debian.org/status/package.php?p=libkqueue&suite=sid

The error was:

src/linux/platform.c: In function 'linux_eventfd_init':
src/linux/../common/../linux/platform.h:29:31: error: 'SYS_eventfd' undeclared (first use in this function)
 # define eventfd(a,b) syscall(SYS_eventfd, (a), (b))
                               ^

More recent architectures do not have SYS_eventfd; they only have
SYS_eventfd2. So the fix is to replace, in src/linux/platform.h,

# define eventfd(a,b) syscall(SYS_eventfd, (a), (b))

with:

# ifdef SYS_eventfd2
#  define eventfd(a,b) syscall(SYS_eventfd2, (a), (b))
# else
#  define eventfd(a,b) syscall(SYS_eventfd, (a), (b))
# endif

Dear submitter,

as the package libkqueue has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1104870

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)