Function forced_site_patching_value 

pub fn forced_site_patching_value(backend: Backend) -> Option<&'static str>

The value of REVERIE_LITEINST_SITE_PATCHING (reverie_liteinst::SITE_PATCHING_ENV) that the guest sees under backend, when Hermit decides it: 0 for in-guest-trap, which exists to run with no syscall site patched, and None for liteinst, which leaves the variable to the guest environment (unset means patching on).