Avoid calling DepIsInSameApex when excluded from apex contents

While debugging an issue with some work I was doing on boot image
modules I noticed that markPlatformAvailability() is calling
DepIsInSameApex() even when the dependency tag indicates that it is
excluded from the apex contents.

Test: m droid
Change-Id: Iac49049546a886f7a3a0d9640ffd31ce24c61364