build_packages: log the pkgs we are about to merge
build_packages: log the pkgs we are about to merge

When running build_packages, the toolchain checking operations from the
update_chroot step and the initial merge are hard to differentiate, so
add an explicit `info` message so people can see what's going on.

BUG=None
TEST=`./build_packages --board=x86-alex` shows more info

Change-Id: I3593eb9ca56c620232bf155daf89b15fadb6547d
Reviewed-on: https://gerrit.chromium.org/gerrit/17604
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

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