cmake: add functions for handling global and persistent variables
cmake: add functions for handling global and persistent variables

Change-Id: Ice07806e6eb079272a4c830b379742568ddf0522

dmerejkowsky/qibuild,aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild