For functions without any calls, there is no value in executing a stack
check. The current frame is materialized at that point anyway.
Note that for loops, we still emit additional stack checks in the loop
header.

For unity, the reduction in code size is moderate (0.53%), as only 4000
of the 34000 functions are leaf functions (no calls). However, we also
save some compile time and gain performance, so this is still worth
doing it.

Drive-by: Fix the effect chain generated in {StackCheck()}.

R=mstarzinger@chromium.org, ahaas@chromium.org

Change-Id: Ia6ec58d0ea46de02634c923cdf8e6e08d8902c59
Reviewed-on: https://chromium-review.googlesource.com/533333Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46013}