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 -Narup uClibc-0.9.30.1.orig/libc/inet/getaddrinfo.c uClibc-0.9.30.1/libc/inet/getaddrinfo.c

 --- uClibc-0.9.30.1.orig/libc/inet/getaddrinfo.c	2009-02-26 21:49:14.000000000 +0900

 +++ uClibc-0.9.30.1/libc/inet/getaddrinfo.c	2009-03-06 00:59:23.000000000 +0900

 @@ -187,6 +187,8 @@ static unsigned __check_pf(void)

  		}

  		for (runp = ifa; runp != NULL; runp = runp->ifa_next) {

 +			if (runp->ifa_addr == NULL)

 +				continue;

  #if defined __UCLIBC_HAS_IPV4__

  			if (runp->ifa_addr->sa_family == PF_INET)

  				seen |= SEEN_IPV4;