aix: prevent stack overflow in RegExp test by increasing available stack size

Change-Id: If22939274db5db07a4f947ef5ef209d96078da36
Reviewed-on: https://chromium-review.googlesource.com/c/1351766Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#57942}

test/mjsunit/regress/regress-crbug-178790.js

@@ -25,6 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --stack-size=1200
+
 // Create a regexp in the form of a?a?...a? so that fully
 // traversing the entire graph would be prohibitively expensive.
 // This should not cause time out.