CBQE-1611:Modify toy-build support for existing install script

Change-Id: I4d2b425bdf6a6b25bcba36adc1d2c626854f4935
Reviewed-on: http://review.couchbase.org/29835
Reviewed-by: Ronnie Sun <ronnie@couchbase.com>
Tested-by: Ketaki Gangal <ketakigangal@gmail.com>