envsetup.sh: don't assume 'cd' is builtin

Some parts of envsetup.sh aren't very happy with things like
this:
function cd() {
    builtin cd "$@" && pwd && ls -l
}

here, I have s/cd/builtin cd/ one such case where envsetup
is trying to execute the output of cd.

Test: manual
Change-Id: I2774481dfbd958410682a4f773f1b8f12a0080aa