This directory is an Ekam-style dependency import. See:

    https://github.com/sandstorm-io/ekam

Since libseccomp is not Ekam-clean, we do a little hack. Normally, configure.h
is generated by the configure script, but we don't want to run that script
here. So we provide our own configure.h. It turns out that there's only one
option in there that's actually used and that option doesn't actually matter,
so, whatever.

Unfortunately, the only way to provide our own configure.h that is available
to all the seccomp *.c files but is not directly includable by the entire
world is to have it be in the same directory, which means we can't symlink
the whole libseccomp/src directory; we instead must symlink each file
separately. Dang.

Luckily libseccomp doesn't appear to change much. We'll just update things
if there's a breakage.

As a second hack, we symlink the original source tree's seccomp.h.in to
include/seccomp-in.h. Since we haven't run the configure scirpt, the version
number macros in this file won't have been #defined correctly, but we also
provide the header include/seccomp.h which includes seccomp-in.h then fixes
the macros. Note that as of this writing, libseccomp actually sets the
version number to 0.0.0 in its configure script, making these macros fairly
useless. Luckily we don't use them anywhere, and libseccomp uses them only
in a function that returns the version at runtime, which no one uses.

We should probably find a less-ugly solution eventually.
