Merge #1552

1552: Make the SIGINT handler conditional on --features "managed". r=nlewycky a=nlewycky

The SIGINT handler was used in the tier switching demo to switch between compiler tiers upon press of ^C in the terminal.


Co-authored-by: Nick Lewycky <nicholas@mxc.ca>
Co-authored-by: nlewycky <nick@wasmer.io>