check_deps: dynamically insert native multilib path
check_deps: dynamically insert native multilib path

Rather than hardcoding every possible multilib path that we might come
across, look up the native multilib path that the target system is using
by finding the native ELF interpreter.  We use /bin/sh as a known good
file since you can't really have a system without this.

BUG=chromium-os:20636
TEST=`./check_deps /build/amd64-generic /bin/bash` now finds libs without explicit ld.so.conf
TEST=`./build_image --board=x86-alex` still works

Change-Id: Ib80824312a5e5a0f9e17e8ae18a2d42248771eb7
Reviewed-on: http://gerrit.chromium.org/gerrit/8564
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

sigma/coreos-scripts,endocode/scripts,marineam/coreos-scripts,BugRoger/scripts,fivethreeo/scripts,fivethreeo/scripts,zhang0137/scripts,crawford/scripts,andrejro/coreos--scripts,mjg59/scripts,mischief/scripts,glevand/coreos--scripts,smilart/scripts,trnubo/scripts,sigma/coreos-scripts,mjg59/scripts,vmware/coreos-scripts,smilart/scripts,endocode/scripts,marineam/coreos-scripts,coreos/scripts,nicescale/scripts,smilart/scripts,BugRoger/scripts,andrejro/coreos--scripts,mischief/scripts,nicescale/scripts,zhang0137/scripts,gtank/scripts,trnubo/scripts,bcwaldon/coreos-scripts,bcwaldon/coreos-scripts,gtank/scripts,crawford/scripts,fivethreeo/scripts,crawford/scripts,BugRoger/scripts,nicescale/scripts,glevand/coreos--scripts,trnubo/scripts,coreos/scripts,sigma/coreos-scripts,vmware/coreos-scripts,mischief/scripts,mjg59/scripts,endocode/scripts,andrejro/coreos--scripts,zhang0137/scripts,bcwaldon/coreos-scripts,gtank/scripts,vmware/coreos-scripts,marineam/coreos-scripts