POSTIN

<lua>

if posix.access("/etc/ld.so.cache") then
  if posix.stat("/usr/lib/locale/locale-archive.tmpl", "size") > 0 then
    pid = posix.fork()
    if pid == 0 then
      posix.exec("/usr/sbin/build-locale-archive")
    elseif pid > 0 then
      posix.wait(pid)
    end
  end
end

Triggers

glibc

if posix.stat("/usr/lib/locale/locale-archive.tmpl", "size") > 0 then
  pid = posix.fork()
  if pid == 0 then
    posix.exec("/usr/sbin/build-locale-archive")
  elseif pid > 0 then
    posix.wait(pid)
  end
end