c-icap: fix config script

This commit adjusts the c-icap config script by removing a bogus
-L$LIBDIR which was expanded to -L/usr/lib, which is wrong for
cross-compilation. It fixes the build of c-icap-modules:

  http://autobuild.buildroot.org/results/b05/b05141a6d450c94669c6a0a5a0f5b799c2c248f2/



Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Guillaume GARDET <guillaume.gardet@oliseo.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>