The TurboFan backends currently don't support tail-calls to CPP builtins
because the semantics of kJavaScriptCallArgCountRegister has different
semantics for stub call descriptors versus JavaScript call descriptors.
This is actually a short-coming of the backends and follow-up work will
make the backends more robust in that regard to fail hard on unsupported
constructs like that. This just disables the lowering creating such a
tail-call.

R=bmeurer@chromium.org
BUG=chromium:658691
TEST=mjsunit/regress/regress-crbug-658691

Review-Url: https://codereview.chromium.org/2447383002
Cr-Commit-Position: refs/heads/master@{#40590}