cros: Enable multiprofile for everyone.

BUG=338941
R=dpolukhin@chromium.org, nkostylev@chromium.org

Review URL: https://codereview.chromium.org/146193005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251352 0039d316-1c4b-4281-b951-d872f2087c98
Introduce the chroot_cmd flag that contains the command line prefix for running in a chrooted environment.

Right now when supplying a 32-bit sysroot via the 'sysroot' GYP flag on a 64-bit host arch,
pkg-config (and pkg-config-wrapper) fail to generate the correct 32-bit paths within that sysroot.
The solution is to chroot into that directory and run pkg-config from there.
This is intended to work with schroot scripts like 'precise32' generated when running build/install-chroot.sh

BUG=324207
R=piman@chromium.org

Review URL: https://codereview.chromium.org/163583003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251353 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251353