This converts the instances of the pattern for which we have a proper
substitution in lit. This will make it easier to replace it
appropriately with Windows equivalents.
We do this by creating a shared function that calls the builtin int_trap.
Eventually I am going to use this to test a runtime bug reducer. But that is for
another day.
Previously, bug reducer tester would just assert when it saw a direct apply to
its target function. Now we add support for also causing a miscompile by just
deleting the apply. This is tested by eliminating an apply to putchar to ensure
we are not dependent on any stdlib details.
