Use PKG_INSTALL_MASK to prevent debug symbols from getting into the binpkg.
Use PKG_INSTALL_MASK to prevent debug symbols from getting into the binpkg.

The mask is set only if it's not set already. Also, it picks up the default
install mask from common.sh.

BUG=none
TEST=gmerged chromeos-chrome with PKG_INSTALL_MASK set/unset.

Review URL: http://codereview.chromium.org/2907005

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