Fix build on OpenBSD with BSD userland emu and smartcard NSS enabled

Fix build on OpenBSD with BSD userland emu and smartcard NSS enabled

The first issue is the hard coded POSIX Real Time extensions library in the
libcacard/Makefile. From looking at the code it doesn't seem this is necessary
anyway. Robert Relyea seems to think it most likely isn't necessary.

The second issue was the missing exclusion of the BSD userland binary
builds from the addition of this Makefile target for the smartcard NSS
code which breaks the builds if smartcard NSS support is enabled.

pastebin clip of the build failure..

http://pastebin.com/raw.php?i=BLCKd3s6

Signed-off-by: Brad Smith <brad@comstyle.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>