Conditional flags for tests - set JS stack size for simulators.

There are separated JS and C stacks on simulators so for some stack
extensive tests (like mozilla/js1_5/extensions/regress-355497) might
cause a C stack overflow and that overflow is not caught by V8. It is
not an issue on real HW. Increasing the C stack also solves the problem
but we have already FLAG_sim_stack_size flag to control the JS stack
size.

This patch makes it possible to add flags to tests conditionally in
.status files.

TEST=mozilla/js1_5/extensions/regress-355497
BUG=v8:3152
LOG=N

Review URL: https://codereview.chromium.org/735723006

Cr-Commit-Position: refs/heads/master@{#25434}