Assertion failure on system with 64k page size

Created by: fhahn

On a system with 64k page size, a bunch of nightly tests fail http://dynamorio.org/CDash/viewTest.php?onlyfailed&buildid=26475

<-stack_size must be at least 12K and a multiple of the page size>
<Application /home/dynamorio/nightly/run/build_debug-internal-64/suite/tests/bin/common.allasm_aarch64_isa (8781).  Internal Error: DynamoRIO debug check failure: /home/dynamorio/nightly/src/core/options.c:983 false
(Error occurred @0 frags)
version 6.2.17363, custom build
-no_dynamic_options -code_api -stderr_mask 12 -stack_size 120K -max_elide_jmp 0 -max_elide_call 0 -vmm_block_size 64K -initial_heap_unit_size 192K -initial_global_heap_unit_size 192K -heap_commit_increment 64K -cache_commit_increment 0x10000 -early_inject -emulate_brk -no_inline_ignored_syscalls -native_exec_default_list
0x0000ffffe3746660 0x0000aaae07ff1da4
0x0000ffffe37467f0 0x0000aaae07f407d0
0x0000ffffe3746a30 0x0000aaae07f436cc
0x0000ffffe3746a70 0x0000aaae07f437a4
0x0000ffffe3746a80 0x0000aaae07f5a150
0x0000ffffe3746aa0 0x0000aaae08245904
0x0000ffffe37472d0 0x0000aaae0820eb38>