This is off by default, but enabled by the parser when reading a textual
IL file. Test files can still override the default to turn off
verification.
The setting enables IL verifier passes at critical points of the
compilation pipeline.
The intel, arm32, and arm32 targets were only defined in the meta
language previously. Add Rust implementations too.
This is mostly boilerplate, except for the unit tests in the
registers.rs files.
