Fix linux+arm64 build after 8254072

/home/beurba/work/jdk/src/hotspot/cpu/aarch64/sharedRuntime_aarch64.cpp:1501:52: error: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'int' [-Werror=sign-compare]
 1501 | assert(StackOverflow::stack_shadow_zone_size() == (int)StackOverflow::stack_shadow_zone_size(), "must be same");