Socket::MsgHdr is only packaged for Debian and derivatives at
the moment, and Inline::C pulling in gcc/clang is a huge amount
of disk space and bandwidth for some users.
This enables disk space and/or bandwidth-limited users to use lei.
Only Linux guarantees a stable ABI and syscall numbers, but
that's the majority of our userbase. FreeBSD users will still
have to use Inline::C (or get Socket::MsgHdr packaged).
x86, x32, and x86-64 are all currently supported, more to be added.