Ensure that a valid off-heap trampoline is created for the
GenericJSToWasmWrapper builtin by adding it to the list of executable
builtins.

R=ahaas@chromium.org
CC=​evih@chromium.org

Bug: v8:10701
Change-Id: I49b8144237aca20f5f663c7b32810a16f715ad5f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2438415
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70218}