gradm: fix gradm_pam path

We alredy rewrote /sbin/gradm, which technically matches
/sbin/gradm_pam, so this ends up working exactly as we want. Otherwise
we rewrite twice and gradm can't execute the PAM module with '-p'

Signed-off-by: Austin Seipp <aseipp@pobox.com>
gradm: learn of all accesses for /nix/store

This is necessary for gradm's learning mode to work, as otherwise the
/nix/store directory is marked hidden, which causes the kernel to reject
the linker loading ld-linux.so

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixos: make several kernel common-config options optional

Realistically, common-config is useful, but there are a lot of things in
there that are non-optionally specified that aren't always useful. For
example, when deploying grsecurity, I don't want the bluetooth,
wireless, or input joystick/extra filesystem stack (XFS, etc), nor the
staging drivers tree.

The problem is that if you specify this in your own kernel config in the
grsecurity module, by saying 'BT n' to turn off bluetooth,
common-config turns on 'BT_HCIUART_BCSP y', which then becomes unused
and errors out.

This is really just an arbitrary picking at the moment, but it should be
OK.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixos: add grsecurity module

Signed-off-by: Austin Seipp <aseipp@pobox.com>