common.sh: fix pkgconfig install mask
common.sh: fix pkgconfig install mask

Since pkgconfig is installed in the native libdir path, we need to
make sure to filter out all pkgconfig subdirs.

BUG=None
TEST=`./build_image --board=amd64-generic` no longer includes .pc files

Change-Id: Id8116190b6900ac86b433794551b250b6445d9d8
Reviewed-on: https://gerrit.chromium.org/gerrit/29682
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

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