scripts/gcc: Canadian Cross skip -print-multi-lib log output

Attempting to ${CT_TARGET}-gcc -print-multi-lib will fail

In do_cc_core_backend, for the final compiler in a canadian cross
baremetal, warn that multi-libs cannot be determined

In do_cc_backend, for either final compiler for a canadian cross,
warn that multi-libs cannot be determined

(Plus fixed CT_PREFIX_DIR in do_cc_backend to be ${prefix})

Signed-off-by: "David Holsgrove" <david.holsgrove@xilinx.com>
Message-Id: <CAM=EW8aQDoNx-CkJHjXBoDP4iTDJ8z5hh3=KhO5UTU6rp3Pj=w@mail.gmail.com>
Patchwork-Id: 189053

diff -dur strace-4.5.15.orig/net.c strace-4.5.15/net.c

--- strace-4.5.15.orig/net.c	2006-12-13 20:57:23.000000000 +0100

+++ strace-4.5.15/net.c	2007-07-14 19:29:36.000000000 +0200

@@ -800,8 +800,12 @@

 #ifdef SOL_PACKET

 static const struct xlat sockpacketoptions[] = {

+#if defined(PACKET_ADD_MEMBERSHIP)

 	{ PACKET_ADD_MEMBERSHIP,	"PACKET_ADD_MEMBERSHIP"	},

+#endif

+#if defined(PACKET_DROP_MEMBERSHIP)

 	{ PACKET_DROP_MEMBERSHIP,	"PACKET_DROP_MEMBERSHIP"},

+#endif

 #if defined(PACKET_RECV_OUTPUT)

 	{ PACKET_RECV_OUTPUT,		"PACKET_RECV_OUTPUT"	},

 #endif