ART: Configure stack guard size in the Makefile

Configure the stack guard reserved size through defines set in
the Makefile. This can be used to increase the gap depending on
the configuration, which may be required to safely support Java
stack overflows in instrumented builds.

Bug: 30766843
Change-Id: Icdd3209e3a261ea8383ef8eab38153255339b04a
Test: m test-art-host